I finally got to build stores in my settlement. I have tried assigning multiple people to stores and waited, fast traveled, and tried going different times of the day. They are never at the stores.

Anyone having this issue or know a fix? Am I doing something wrong?

I finally got it to work but... Now I don't know how to buy and sell. It gives me an option to trade but no go to the actual store..

You click the "Barter" option.