Install
(After you've downloaded AdminPad) navigate to Extensions > Install/Uninstall, browse for the tpl_adminpad_v#.zip file and Install.
Set to Default
Navigate to Extensions > Template Manager > Administrator. Click the radio for adminpad and click Default in the top right.
Set AdminPad to iPad only (optional)
If you'd like to continue using your current Admin template, navigate to Templates > Administrator, edit adminpad (or go to Admin Parameters) and set Browser Specific to On and pick your admin template.