First - Logon to your Google apps account using your domain admin user ID and password, then follow the steps written below.
1. Goto https://tandem.cc/ and click on 'SIgn Up' button
2. Click on the button for Domain installation
3. Click on 'Install App'
4. 'Accept' all the permissions
4.1 Click 'Next'
4.2 Click 'Next'
4.3 Click 'Launch'
5. Tandem Console opens as follows
Incase you forget to click on the launch button you can goto to your google apps admin console and activate Tandem