I would say that children's books are a bad place to start unless you're going to have someone read them aloud to you (while pausing for effect, making sound effects, et cetera) and then you read them yourself.
Stay away from picture books, even if Alan Moore's name is on the cover.
With that out of the way, this is going to take some work. For your situation I would recommend:
1. Picking a play you've never seen live or adapted as a movie. Stick to something recently written if you can instead of high theater or Ancient Greek stuff.
2. Grabbing a printed copy of it. If you have access to a local library it's probably better to check out a copy from there because plays are usually overpriced.
3. Read it with a pen and paper by your side. As you go along and when you finish a scene write down:
-how things make you feel when they make you feel something. it doesn't have to be anything intelligent or even coherent, I think I have "damn Creon be fronting rn" written in a copy of Antigone somewhere.
-what you think someplace or someone looks like (written plays have minimal description usually). think about what people say and how you think they're saying it. don't be afraid to have a bad dude dress in black or whatever.
4. The prior step will take you awhile to complete, I would not recommend completing it in one sitting.
5. Wait a few days, read all of your notes again, then try to read the play in one sitting without stopping to write notes. Use what you felt and imagined in your first read to fill in the blanks.
6. If you can, see the play live or as a movie adaptation. Think about how you pictured things versus how the production team did it. If they disagree, why do you think they pictured that thing in that way?
If this all sounds very repetitive keep in mind that we had our parents, teachers, other adults read us the same stupid books over and over as kids.
