Hi I have a Capacitor start and run motor, how can I wire it to run forwards and backwards via a on/off/on s/w?

There should be a waiting diagram on the plate covering the wire connecting spot. Check to see if it is possible. Some ACmotors can be reversed other cannot.

Like mentioned above, some can't be easily done.
Many of the ones that do, like davits or operators that use a reversing contactor for reversing.
Basically many of those motors have 6 wires that need to be connected correctly for voltage and use 4 of those wires to hook to the davit switch which for a 120 volt motor place 120 voltas on 2 of the wires and 120 volts to the other 2 wires, and when you reverse the 120 volts on either pair, it reverses.
1 Davit switch/ drum switch will work.
Or if you want to use a small toggle for control, you need a SPDT switch, a reversing contactor, 24 volt transformer, and a motor that can be reversed.