Bring your bike to the shop. Saddlebags are a significant investment, so it's worth it to make sure they fit just right. The salesperson should allow you to take the saddlebags out of the store and look at them next to your bike. Beyond appearance, make sure the saddlebags do not hang over the shocks or too close to the wheels.
Pack the saddlebags. While you may have a description of your saddlebags, complete with storage measurements, try them out with your gear. Saddlebags should be able to fit at least your jacket, a water bottle, a change of clothes and a bottle of oil.
Remove the motorcycle seat. The seat should lift away easily after removing screws on the front and back.
Dangle arch straps of the saddlebag (the straps connecting the two bags) over the seat frame. Align the straps so they do not interfere with any part of the seat used in connecting the seat to the frame.
Reattach the motorcycle seat. Replace screws and adjust the saddlebags periodically while tightening the seat back in place.