Which tunnel? The tunnel in Kanto or the one in Goldenrod City? The one in Goldenrod you get to by going the the left of the renaming tent...the little blue building, you know? The other one is a bit more complicated to get through.
you have to go to the under ground tunnel and you will see someone team rocket talk to him and hell give you uniform and then they will let you pass your welcome
go in the golden rod under ground tunnel
if your talking about the team rocket uniform that's under ground in goldenrod (the place where you get accesories for your Pokemon)
digging under ground,o course.
They're in the trash can
you can get a mareep under viloet city
yep but its gonna be extremely hard!
you get the tea from the old lady in the city with the casino and you give it to one of the guards near saffron city and then all of them will let you through.
go under ground and find fossils
you go under ground from a tunnel around it
you have to go the kanto region under lavender town.
under goldenrod city