Hi, and welcome. To access the advanced settings (aka dosbox.conf), simply scroll down to the bottom of your game profile settings. Tick the “Expert commands” checkbox on the bottom left, then the cogwheel icon on the bottom right, and put whatever commands you like in the conf file.
Don’t forget to accept your changes afterwards, and save your profile.
If you have specific questions about a certain game, you can post them here, along with the settings you’ve tried so far, amd we’ll figure out how to run it.
Basically, every game that works on the PC version of Dosbox will also work in Magic Dosbox.