Ok so, I have a Projects Table and an Employees Table. First I keep getting very confused how I should set up the PK and FK in general. 

I have Customers table and I want it so 1 customer can have multiple Projects at a time. So the solution is to put CustomerId into the Projects table and make it a foreign key right?

So the problem is, I want multiple employees to be a part of projects at any given time, and obviously each Project will need multiple employees. How do I set up Referential Integrity between them?