I added a new ADO.Net Entity Data Model into my project and used the Update Wizard to add tables into the model. Five of the selected tables were added to the design surfac
One easy way I found was to (in SQL Server Management Studio) add an ID column of type INT, deselect "Allow Nulls", and under Column properties (of ID) >> Identity Specification >> check (Is Identity), and make sure increment is set.
Once the above is done, go back to your .edmx window, right-click, and Update Model from Database.