1989 Accord pulling timing belt back onto pully

Thank you for taking the time to read my email. I have jsut finihsed changing my head gasket on a 1989 Honda Accord, 4 cyl engine, 260 000 km. I am re assembling the the engine and have only to pull the timing belt back onto the pully, but its a tight fit, do u have any tips? I have tried removing the pully and placing the belt on it first and then pushing the pully with belt onto the side of the head. However the small pin keeps slipping out and its quite tight. Do I haveto remove the wheel and go in from the bottom and loosen the bottom of the timing belt?

thank you again for your time, I look forward to your reply

Brian