beat Giovanni in saffron, beat the 7th gym finish the quest on the islands and go to viridian city. the gym over there is the 8th gym.
it is in veriden city.
The seventh gym is on Cinnabar island,right down of pallet town.To open the doors you must reach to a certain room of the Pokemon mansion.You get a key and open the seventh gyms doors,and the gym is a fire gym
In his gym
the 5th gym is saffron gym with sabrina!
Misty
wermilion city gym badge (electric type gym)
Sabrina's gym in saffron city
Use the HM surf and go south from pallet town you will eventually reach cinnibar island the gym is locked though to open it find the key in Pokemon mansion.
I think the gym in fuschia city
It depends on what gym you are talking about all of them you can get to by going to the towns.
in the mansion.
In Cerulean city.