Hi Deanna,
LOA privileges are assigned from within the portal once a user has been given either the CBR User or CBR Admin role using CSAM.
You are correct that this will not be possible until there is at least one inventory in place since the menu (including the Admin Dashboard) does not fully populate until then. While it may appear inconvenient, there is actually no point to getting LOA privileges until there is data in the portal since LOA allows the user to view contract data. If there is no device data in the portal, then there is nothing to access.
Instructions on how to grant LOA access are included in this video: http://www.cisco.com/E-Learning/bulk/subscribed/SNTC_vods_EN/Access_Control.mp4
You can find the full video library here: https://supportforums.cisco.com/community/12286826/how-videos
Thanks,
Nathalie