In the Backup Exec Administration Console, go to Tools/ Install Options and License Keys on this media server. Navigate through the prompts past your license information to the Backup Exec Option screen. Select the Advance Open File Option on this screen. Click next through the install.
You will need to install the AOFO client on your remote servers as well. To do this go to Tools/ Install Agents and Media Servers on Other Serves. Go through the process as before to install the remote agent but this time select the option for AOFO as well.