I'm planning on making a check-list with checkboxes but I don't know how to code it so that you can uncheck and check them I also don't know how to save it. Like when you go to another screen and go back to it you can still see it checked or unchecked. I barely know anything about coding yet so help is greatly appreciated!
Here are some resources to help you learn to use the AI2 tools. A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
If you expect the number of check boxes to grow, you will need to switch to a list based approach, where you keep lists of the text values of the checked checkboxes and the non-checked checkboxes.
A single ListView or List Picker can act as a bunch of checkboxes.