The Manual

« Section 6 »

6.1 Admin Users

GlotPress has a different set of administrative users than WordPress does, so a user with the “Administrator” role in WordPress does not automatically have administrative privileges in GlotPress. Likewise a user does not have to be a WordPress administrator to be a GlotPress administrator.

During installation, the user you installed GlotPress with was marked as a GlotPress administrator, by default this is the only user with administrative rights.

Once installed, you can assign other users (or remove admin rights from a user) through the WordPress user management interface.  Simply edit a user and the following section will be present:

You can either check or uncheck the tick box to select if the user is a GlotPress administrator.