The process should work like this:
1. go to settings -> views and menu bars - add a new user
2. choose individual or group (they work the same way) and you'll see this screen - slightly different for each, functionality is the same though:
3. choose a name to search for - and enter the domain admin credentials to access the list of AD accounts. To do this, your credentials will need to be a administrator - member of the DomainAdmins group.
4. on the next screen, you'll see all the AD accounts that are available to be imported. Choose the ones you want.
5. all of these users will be given accounts in EOC.
Functionality that Orion is currently working on will make it so those newly imported accounts will (optionally) automatically sync up with their Orion AD accounts, so those users will automatically have rights into those Orions from EOC.