SQL DATABASE ENGINE permisions
Since the application is running on user workstation, it is likely to be run on user's own account. This, unfortunately, means you are out of luck with the simple solution - setting up user permissions.

What could work is an approach based on stored procedures with EXECUTE AS. 

There are lots of tutorials in the net. For a summary:


Create a user account for application usage and grant it appropriate rights to the database objects.
Create stored procedures to handle all the required data operations. Use
EXECUTE AS to run those procedures as the application user.
Grant your users rights to execute the procedures.
Revoke other permissions from the users.