I have purchased plants that attract bees, but I have not seen any bees, I do not know what to do with the vegetables I have planted that need bees to produce any advise?

Previous answer is correct bees will pollinate one type of plant and not jump around..Bees travel up to 4 miles for pollen. With all of the chemical sprays we don't have an over abundance of bees.

Plants that attract bees attracts other polinators as well. Such as butterflies, etc. And maybe there aren't any bees looking for that particular plant. Another thing to consider; if a bee goes to an avocado tree (for example), it will stay pollinating avocado trees all day long. It will not hop from one flavor to another.

Buying a bee hive with bee's will help you a lot