When I first installed the new AADSync tool, I struggled to figure out how to force a synchronisation. In the first release of DirSync, you would use the following commands from an Administrative CMD prompt to force a sync:

cd "C:\Program Files\Microsoft Online Directory Sync"
.\DirSyncConfigShell.psc1
Start-OnlineCoexistenceSync (optional: -FullSync)

Then DirSync was upgraded to version  6862.0000 and the process changed. First you opened a Powershell prompt (as Administrator, of course) and then ran:

Import-Module DirSync
Start-OnlineCoexistenceSync (optional: -FullSync)

In the new AADSync tool, the process has again changed. There is now a task in Task Scheduler called Azure AD Sync Scheduler which controls the running of the AADSync tool. The FullSync parameter used to force a full synchronisation, but you now use the Initial parameter to do this. You can force a sync by opening an Administrative CMD prompt and running:

cd "C:\Program Files\Microsoft Azure AD Sync\Bin"
DirectorySyncClientCMD.exe delta (optional: initial)