How do you catch moltres in Pokemon Red and blue?

once you have defeated all eight trainers and are on your way to the indigo plateau you will hit a cave, this cave is named victory road,(or so i believe) while in that cave you will come across a frog looking Pokemon in a spot, there are numerous guides i am sure to find the Pokemon once in there, one of my favourite guide/walkthroughs from Pokemon red/blue are "kodys kick ass Pokemon red/blue walkthrough" this is a good walkthrough, so go you YouTube,

look up

"Kodys kick ass Pokemon red/blue walkthrough finding moltres" its a good guide and i trust it, hope this was helpful!