Basically, you pick a Gym Leader you like (like Morty) and then you check the "Johto" section of the list of Gym Leaders. You scroll down until you find Morty then you pick some of the Pokémon there to be part of your team. The rest is easy, just follow the rules in the thread
If you wanna do a Gym Leader Challenge, you miiight wanna try here.
The thread you posted in was long dead. Threads that got no replies in 2 months are considered dead. That thread got a last reply in 2010 xD So yeah xD