Place your bike on its kickstand or a repair stand. This will stop the bike from moving and allows you to quickly and easily get around the bike and perform repairs. The kickstand will work as well, but a repair stand is much safer and gets the bike off the ground.
Feel around the back end of the seat on the bottom side of it. There should be either a latch or two bolts. The bolts will be on each side holding the seat to the frame. If there is a latch, you easily can just pull back on the latch and the seat will come off with a gentle tug. If there are bolts, you must use a wrench set.
Take the proper size wrench, which is most likely a 1/2 inch and loosen the bolts on both sides. Be careful to watch the bolts as they might fall out and be hard to find rolling on the ground. After loosening the two bolts, take them out.
Lift up on the back end where you just removed the bolts and tilt the seat up until the front of the seat is released near the handlebars. Then you can continue to lift up until the seat is completely removed.