Well these are devices with a bazillion settings and can be used in many ways. I've lost count how many routers I've configured as a WAP but that wasn't your question.
I think the problem is that while I could answer how to do that in a paragraph the paragraph might only make sense to those that have been networking for about a year. I know I didn't know how to do this years ago.
So there it is. A technical product that does not come with full documentation for reasons we know but rarely write about. That is, head to a brick and mortar book store and marvel at the number of books on networking. To explain how this works may take a few books.