Mixers generally connect with RCA cables as far as I know, (red and white audio cables). You will probably need some kind of adapter unless you have a dedicated sound card with RCA connectors.
Some more expensive/newer mixers may allow the use of an Optical Audio cable. Again this depends on the mixers connections, and the sound cards.
RCA (with 3.5mm AUX): http://www.blueunplugged.com/dbimgs/3.5-STE-RCA-5M-prod.jpg