Pretty basic
Text tut
Go to your teknogods mw3 folder>go to teknogods.ini(under steamclient.dll)
de35a60fb14b55c324cf5d344c7e14da.png
open it, under [settings], it says "name=" which is the name you will be using while playing, just change it to what ever you want and click file>save
thats it
video tutorial