I am attempting to add an additional device, (I am a premium member), and I can find no way to assign a custom name to antitheft. I’ve uninstalled everything, reinstalled Mobile security, selected Anti-Theft (Install) and it goes straight to the Anti-Theft installation program, there is no option to select “advanced installation” so I cannot assign a custom name to Anti-Theft… HELP!!!
You are given an opportunity to chose an alias for avast during the setup installation.
Make a note of it. That’s what you need to launch (logo green android) after the setup is complete not the avast (avast logo).
If you’ve already gone through the setup installation you may have been a little tap happy with the ‘Next’ button and gone past it…
Has a new Icon (green android) appeared in your apps (home screens or all apps)?
Obviously you missed the point where I said I’ve “installed and reinstalled” in fact, I’ve done it repeatedly, …
No help on this Forum, guess it’s time for Tech Support unless a moderator would care to join in… :-\
http://files.avast.com/files/documentation/mobile-security-user-guide-en-v2-4-updated.pdf
See page 13.
And what do you mean with “I am attempting to add an additional device” ?
Maybe you too miss the point, of forums… that people, give up their time to try and help other people. :
Anyway, in summary, the reason you are having difficulties is, YOU’RE DOING IT WRONG. 
You must install Anti Theft version rooted (in Google Play too), not check the box “install root” and chek “continue” voilá!
I’m not being argumentative, just being curious, what if you want a rooted install? Is your method a work around for a bug or is there reasons this works. I only have AAT installed on its own, I don’t have any other avast security apps installed, I assume this makes some differences to the AAT setup?