i just got my behringer xenyx 802, and i just started recording at home so im not real experienced. i plug it in through a m-audio moblepre. my question is, what exactly do i do with these knobs? my highs, mids, lows, fxs, and levels, how should i set them??

I have the little brother of the 802, (the 502), and you made a good pick.

The knobs are grouped by channel (source of input).  High, mid and low basically control the respective frequencies of your input sound.  So if you increase the low knob, your sound will become bassier and have a more prominent low end.

The levels are basically the amplitude of the sound.  I would suggest setting your Main Mix to 0 (bang in the middle), and start playing, whilst slowly increasing the level of each channel.  The magic point is getting to where your input gets as high as possible without clipping.

I'm not familiar with the 802's FX, check the manual.

As for setting all of these, it really depends on the instrument you want to record.  I'd just experiment with whatever sounds good.  Just make sure you don't make anything in the extremes (highs, mids and lows).

Good luck!