Hi, no problem. ?
The .mgc files are exports of game profiles other users have uploaded here on the forum. You can import them into Magic Dosbox by tapping the “+” icon on the left side, then “Import profile”. Navigate to the folder where you’ve stored the .mgc file (most likely just /Download on your sdcard).
You will have to adjust the mounting commands, because naturally, the person who uploaded the profile is using a different folder structure for the games than you.
Apart from that, all other settings, most importantly the control widgets, will all be setup automatically.