Help with roles

Hello everyone,
I just wanted to ask you about some role stuff
I installed role scoper but have no clue how to use it, it is extremely complicated.

I have a category called “board” and a user “boarder” and I want to make it so that this user can only post to this category, no other category.

If possible, i would also like to make it so that no other user can post to this category.

Now, what do I need to do in order to make this work?

Many thanks in advance for the help 🙂
Jonáš