At the top of your screen go to File → Administration.
Click to highlight the user whose credentials need modified. Scroll through the list of permissions on the right-hand side of the window. There are multiple different permission options for each task. In some cases, you may want a user to be able to view a section but to not make any changes. In this case you would just click on the View box. Other options include the ability for a user to Add/Change/Delete records, and to Print. You can give the appropriate permissions to each user. You also have jump button to Turn On All Permissions/Turn Off All Permissions for all sections and for each individual section as well.
Save all your changes at the bottom of the window.