The problem is, of course, that you cannot simply decide to care about something. If you do not care about something, your will cannot simply establish a caring relationship to that thing. It is rather a question of being open to possibilities of caring
The most important active step you can take to cultivate your curiosity is probably to seek out the topics that engage it. Few adults are equally curious about everything, and it doesn't seem as if you can choose which topics interest you. So it's up to you to
"A well-fed man keeps and calmly gives forth his infinitesimal portion of eternity. It sounds big in the summer night. And it is, as it always was down the ages, when there was a man with something to tell, and ones, quiet and wise, to listen." - Ray Bradbury