Not knowing the engine
model, etc. the 2 bolts should allow the solenoid rear to separate from the starter. The solenoid is a big electromagnet. When it comes apart, a round piston/like object will withdraw . It will have some linkage that pushes the starter gear
into contact with the flywheel gear
. The linkage may have to be disconnected to withdraw the piston.
Also, the solenoid is a high amp set of contacts. Sometimes when a starter fails, those contacts have become pitted from arcing. On a heavy duty solenoid the contacts are heavy brass and can be filed smooth again. If nothing else is burnt out, the starter will work again.
One of my generators is a Onan. I got a replacement starter on Ebay for $65. The dealer wanted $245.