1st this doesn't even need registration, just give a name of the army, choose a trooper and there you go.
2nd if you explain it it sounds actually pretty boring:
You will get into fights with other armies, and earn credits through this. With credits you can upgrade and recruit your troopers.
You will unlock more battles and perks for your troopers by time and credits, and if you invite someone to join your army you will unlock the RAID-mode, receive 100 credits and if you invited 5 others you will unlock EPIC-mode.
Ok that sounds boring, but it's somehow addictive, i just can't get away from it.
Only perhaps bad point: You can only do fights every day, so there are 3 normal fights and one mission with three tries and in raid-mode many waves until you loose one fight, (dunno about epic-mode yet) and if you fought all those you'll have to wait until the next midnight before you can declare war again.