It's impossible without cheats and I'm quite sure Pokemon indigo is pirated which basically means it's fake.
You Get It By Trading
mew doesn't evolve
Mew can be found in Olivine City where Jasmine is.
go to room 131915
in one of the johto cities.
you could go to rooms and type in mew in the room name
Go on the PK Locator and search Mew. There should be many rooms.
On the 1st gym of kanto
Your question has been easily solved! Answer : Through time the makers of it put mew available in rooms.
ceruleon cave i hate to say it but whoever created this awnser was thinking of the Pokemon games for gameboy/advance. now i will tell anyone were mewtwo and mew are if they send me IC$10000 Pokemon indigo credits. my usename is burrmab
i dont even know lol, but i know with it you can get mewtwo and mew
if you want a mew then add me (I'm called pokemeddler or yu-ke-io) and we'll negotiate the price