hey man, basically the ART MP is purely a "Preamp" which will amplify the signal from the mic (or whatever is plugged into it), but to get it in to the computer you need an analogue to digital convertor (A/D convertor) to turn the amplified mic signal into one the computer can read. there's a couple of options, all of which will vary in quality;
the cheapest/simplest but worst quality - buy an 1/4 inch jack to mini jack and plug it from the "line out" of the ART Mp into the "Line in" on your computer (in this scenario the built in sound card in the computer acts as the A/D convertor)
the next cheapest and results may vary in quality - buy an XLR to USB cable (in this scenario the cable acts as the convertor)
the most expensive but best quality and most options - buy a budget audio interface (there's plenty out there in the £70 to £170 price range) this is basically a separate box that will do a number of things, but most importantly in this case, it acts as a A/D convertor. they also act as a D/A convertor so you can plug headphones and speakers into the audio interface as well that means you can monitor the sound you're recording directly without any delay (latency) as well as playing back any pre-recorded material through the same system to play along to. they also often come with at least one or two pre amps built in as well which opens up your options for recording one or two things at a time on separate channels.
the A/D conversion in built in PC sound cards is not really meant for recording audio. often it's meant to deal with, at most, a headset mic or equivalent for online gaming or skye etc.
any of the above suggestions will work, but as i said, the quality will vary.
also, what software (DAW) are you planning to record into?