How do you get mewto in Pokemon FireRed?

Answer 1

you can get mewto by finishing the league going to the islands and then getting the blue orb or red orb after give it to the place where bill got you the map and other staff from and then get the three legendrie birds articuno zapdos and moltres after all of that a cave will be opened you need to go to the place where you were you get antei use surf go side a cave will be opened go inside there and you will see a small light but if you use flash then you can use it clearly after you get him and then you might have some plans to do or you can battle the league that's it i will send some more for you.

Answer 2

first get the ruby and sapphire and give it to celio after defeating the elite 4.then go to cerulean cave where the guy is blocking it hes gone.finnaly go inside the cave figure out the puzzle and at the end is mewtwo