This module provides the admin the ability to approve items after the user has uploaded them.
This module may be downloaded from the codex here.
To install, extract the "approvalqueue" folder from the zip file into your Gallery 3 modules folder.
Afterwards log into your Gallery web site as an administrator and activate the module in the Admin -> Modules menu.
You'll need to add the approvalqueue block in to your sidebar as you do other sidebar modules