I would just take the seat out if you can't fit, it's only four bolts and it makes life so much easier while doing this. Anyways for the clutch adjustment you will need a 12mm open end wrench to loosen the jam nut. Adjustment consists of turning the rod so it screws farther into the master cylinder. Note that even one full turn of the rod will make a difference and make sure you tighten the jam nut after adjustment is complete. Let me know how it works out for you.