play red or blue until you get HM02 Fly from the house west of Celadon City (or just beat the third gym and get the badge that lets you use fly out of battle and trade pokemon that know fly to the new game).

IMPORTANT!!: DO NOT fight the following trainers:
The Youngster with a Slowpoke (level 17) on the road to Bill's house(Route 25). He is the fourth trainer after you cross Nugget Bridge, standing directly above a female trainer and facing north.
The Gambler with two poliwags and a poliwhirl (all level 22) between Lavender Town and Saffron City (Route 8). He is standing just east of the entrance to Saffron City, facing north toward the door of the Underground Path. Care fully follow the series of steps illustrated below...

Make sure you have a pokemon that knows FLY. Make sure you have a level 5 or 6 pokemon and a pokemon that knows SLEEP on your team. Stock up with pokeballs (Great Balls work the best). Now Save your game before you enter Route 8 since saving after this point will disrupt the procedure.

On Route 8, stand in front of the door of the Underground Path (don't let the gambler see you or you will need to restart where you last saved). Walk down one step and IMMEDIATELY press start. If you succeed, the menu will pop up before the Gambler "sees" you. Go to the Pokemon list and fly to Cerulean City. The Gambler will see you just before you fly away. Your Start button will no longer function. Go north across Nugget Bridge and head east until you find the Youngster described above.

If you walk right up to the Youngster, the game will lock up, so you'll have to let him see you and walk up to you. Defeat his Slowpoke(afterwards your start button will work again), then fly to Lavender Town. Head west into Route 8. As soon as you enter the narrow path, the menu will pop up by itself. Press B to exit. . . and a wild Mew should appear. Mew will be at Level 7 and its only attack will be Pound.

could u post how to get celebi

easy just......ok get red version it HAS TO BE RED and talk to the the guy standing next to the gym in viridian and then go to cinnibar by flying, fly to vermilian andtalk to the guy that gives you the bike voucher