Which one are you running 2.3.5 or 2.3.6?
If you are sure you want to root your phone be advised that everything will be at your own risk. It will also void your warranty I'm told.
This link has information on how to root your Atrix 2:
UPDATE[02/12/12] The Beginners Guide !!! (NOOBS)[ALL IN 1 RESOURCE GUIDE] - xda-developers
Title of article: UPDATE[02/12/12] The Beginners Guide !!! (NOOBS)[ALL IN 1 RESOURCE GUIDE]
It tells you how to root 2.3.5 or 2.3.6.
To download BootStrap, I downloaded straight to my phone. This is where you find the link.
Also when ready to start the root, you need to go to Settings, Application Settings and check "Unknown sources"
then tap on "Development" check "USB debugging" and "Stay awake".
When you connect to computer make sure you use USB port in back of PC.
Once connected to pc slide notification down and select "Charging Only".
I'm sure their are some out their that are way more knowledgeable than I am, just give them time to respond. Good Luck
I to am new at all this but I found the information I need. Hope this helps. If you really want to root your phone be careful. It's all at your own risk.