K-30 manual mode question.
There is a menu option to 'enable aperture ring' which needs to be set to 'Yes'.
Once you have done that you do the following:
set focus to manual
set exposure to manual
compose / focus your shot
press green button - this stops down the lens briefly and sets the correct shutter speed based on the aperture / ISO you have chosen
There are more detailed descriptions of how to do this around - I'll see if I can find one.