There's lots already written on this - do a search.
But tl;dr is that the Marks put the BMT knobs BEFORE the gain, rather than after. This means that your settings on those knobs are more akin to boost settings in front of an amp, and the GEQ settings are more akin to traditional, post-gain knobs.
Turn treble up and mids & bass down, on the knobs - because treble controls gain, it's a middy amp, and bass before gain just muddies the distortion.
Tune the GEQ to taste to actually shape the tone, but because it's already middy, you'll want to cut that middle slider at least. Add bass to make up for the pre-gain cut, and add treble to taste (many add none on that last slider, and just a bit on that fourth slider).