if its a newer OS 4st engine then OS recomends using a electric starter,just make sure there is fuel in the line and apply the starter to the prop spinner after attaching the glowstarter and after a few revolutions it should fire right up.
don't over wet a newer OS engine or it will just flood it, just make sure there is fuel in the line the engine will draw the fuel when you spin it with the starter,as well read the manual and follow the instructions for starting and break in procedure,if its a older engine and you don't have the instructions you can get a copy from hobby services@ www.towerhobbies.com they will send it to you via e-mail just let them know exactly which model engine you have.
also get a tach a necessary tool for getting the proper rpms over reving a 4st is fatal to these engines when you get it running properly and in tune there great,I have 4 of the OS 4st motors they are solid engines.