The user.cfg file is placed in the C:\Users\[username]\Documents\My Games\Crysis Wars\MWLL\Client directory. 
(Replace username and/or drive name with your current Windows username / Windows installation drive.)

To easily browse to the correct location, start the MWLL Launcher and towards the bottom left corner of the MWLL Launcher,
 click Open User Data Folder. In the Explorer window, double click MWLL and then double click Client.

Alternatively, you can browse to the correct folder by cut/pasting this into your Explorer window: %USERPROFILE%\Documents\My Games\Crysis Wars\MWLL\Client

Please refer to https://wiki.mechlivinglegends.net/index.php/MWLL_Performance_Guide for more details.