you're not racing, right?
chain is on the inner ring? chain/RD are set to the smallest cog?
although this all shouldn't be necessary, it makes doing much easier...
Pull the RD body back, with thumb pushing down on the jockey cage, forefinger to pull the wheel/axle into the dropout.(QR rear setup - TA is simpler for getting the wheel in)
if your rear wheel uses a QR, the end knob can resist getting past the RD mount... tilt the rear wheel just a hair to get the knob part in, then bring wheel back to get the NonDrv side into the dropput...