Do you mean adjust the timing or adjust the tensioning on the chain. The second is very easy to do:
1. Find top dead center (remove 2 covers on the left hand side cover and align the "T" on the flywheel with the mark on the case)
2. Carefully remove the plastic cap covering the adjuster
3. Loosen the locknut at the base of the tensioner
4. Adjust the tension by turning the tensioner (center rod in tensioner should be withing .5mm of being flush with the end of the tensioner)
4. Tighten Locknut and CAREFULLY replace plastic cover.
If you need to actually adjust timing then I'd suggest getting yourself the service manual (a good idea anyway). I believe you can find it as a download (do a search).
Edit: Just look here: