I have a craftsman router, but looking at the manual on this page:
http://www.ryobitools.com/catalog/power_tools/router_rotary/R163RTA
it appears that they adjust the same way. The is composed of two major parts: a cylindrical motor and a housing which includes the baseplate, handles, etc. There is a large lever that pinches the housing to the motor. If you unlock that lever, you can make coarse height adjustments by sliding the motor up and down. This should get you 95% of the way there. once you lock it down, you can use the height adjustment knob to fine-tune the height.