How do I get myself to care about things?
Start by paying attention to what you think about over the course of the day. What do you worry about? What do you dream about? If it takes up mental space, you care about it.
Identify the top 3 things that you think about throughout the day. After you do that, think about whether those 3 things are in fact the 3 things that you want to spend the most mental energy on.
Mental energy does not go on forever. Like everything, it has its limits. It's why Steve Jobs decided to wear the same thing every day - he didn't want to waste mental energy on making decisions about what to wear. He decided to reserve that mental energy for more important decisions throughout his day.
Chances are that the top 3 things that you are thinking about do not match what you want to spend the most mental energy on.
Confront/address one of the 3 main issues that you think about so that you spend less mental energy on it. For example, maybe you spend time worrying about that kitchen door that needs to get fixed or that tough question that you have for a significant other or that paper that you want to start writing. Call the handyman, ask the question, start writing. By addressing the issue that weighs on your mind, you will have more mental energy to care about things that you actually want to care about.
First I think it's important to try and pinpoint the integral reason as to why you lack this ability to find worth in things. This is not an easy task; it requires a significant amount of self-awareness that only comes with time, lots of self-reflection and life experience. Some things that may help:
Spend time with people, go out and experience a variety of different environments and situations. Any time you find something you feel worth your attention, make a note of this and look deeper into why you care about that specific thing, whats makes it attractive to you etc.
Try teaching yourself about something, start a new hobby. Try to create something you would find hard to lose in your life. Self-improvement is highly rewarding.
Look into the science of positive thinking and mindfulness meditation. This is not a weird Buddhist teaching. It's just being mindful of where you are in the present time. Sit down, breathe and be mindful of how you are breathing, how it feels to breath, what your body feels like. You can do this with any activity by simply focussing on that one thing. This will help to bring you some peace.
Try to figure out what you want in life. Even if you may not care about it enough to implement strategies to begin achieving a goal, you need the self-awareness of what you could want.
A last note: it may be that you don't care about things due to another psychological issue. Maybe you have depression? This can lead to feelings of aimlessness and that nothing is worth caring about. Although you may find some help on Quora, this kind of question is best asked to a professional. Therapy, counselling, psychological analysis, CBT all can help.
I don't think you CAN make yourself care about something. I'm struggling somewhat wth the same. What I care about and love is not seen as valuable in my family - the arts. So, therefore, I think I have to care about having some job at a lawyer's office or in a scientific field or something, and I really care about music, dance, performing arts. I feel like what I care about has no merit, but try as I might, I don't care that much about those desk jobs, or jobs that have higher earning potential, so I feel like a loser.
I don't know how you can force yourself to care about anything.
I think you would be pretending and living in secret agony if you tried to care about something you have no interest in.
You don't. If you don't care already, you probably won't start caring. Nor will you force yourself to care, because if you had that kind of willpower you wouldn't have a problem.
However.
You can learn to find things you do care about in those things you don't. For example: I was working on a gaming project of immense stupidity. No one in the team cared about it. But there was a tiny aspect that was appealing to our lead developer. So he grabbed it, clung onto it and threw himself at the project carrying this sacred piece of "I DO CARE" into the fray.
I'm not very good at this technique, but I saw it work like a charm!
Depending on your situation you might need to
(re)connect with people. Even if you are on your own, try going to places where there are lots of people.
stop a self-defeating behavior pattern. If there is something that you feel that you ought to pull off, and you aren't, you may be deceiving yourself thinking that you cannot do it, just because it feels easier (in the short term) doing nothing.
find out what you like or what is important for you, and follow that thread. This it not that easy sometimes. Knowing oneself is one of the most difficult things to do, and sometimes you will need ot dig a lot until you find whatever is really important for you.
You might want to read the tale Li, by Nikkos Kavvadias. Think more about the problems of those who are in a worse situation than you, and find a way to do something about that.