Ok so I just entered high school and I am not the kind of person that knows much about sports and I am really stuck in what kinds of after school activities I should sign up for can anyone give me a few ideas

It depends on your interests. Some ideas...
Student Government
Language Club
Debate Team
Mathletes
Art Club
Yearbook
School Paper
Drama Club

I agree with the above answer. It does depend on your interests.

Perhaps there might be a chess or checkers club that might be of interest to you?

Hey yeah I guess I am good at creating or decorating things so I might help out with the year books and stuff THANKS!

If you get some experience helping out with producing the yearbook and maybe the school newspaper, those types of experiences can also be things that might help you when you go to apply for jobs later after you graduate from high school and even college. For one thing, doing extra things outside of your regular classroom work shows that you are willing to do things extra. Potential employers are likely to think more of people who are willing to do something extra. It would show that you have drive, ambition and potential!