How do you evolve your Pokemon?

You have to finnish the game (beat requarza)and watch the credits then go to wishcash there will be a hole you can go in it but takeaway your team it will say stand by click it then you go into the hole there will be a giant plant it will say evolve or will you give me an item (2)if you do you might be stronger thats it

Only give an item if you need it to evolve. Link cable counts as trading your Pokemon.
For example: You have a machoke, and you want machamp. Use a link cable when it asks give an item, or poor machoke wont evolve.

First of all, you must complete story mode by defeating Rayquaza at Sky tower's peak. There will be a cutscene where Gengar is dragging you somewhere and then you will reappear with your partner at the Hill of Ancients. You will begin to dissapear and start to float away in the sky.The credits will play and, soon enough, you will float down and reappear at your team base. The next day, go to Pokemon Square and visit Whiscash Pond. Snubbul will have evolved into Granbull and there is a hole at the end of the steps. Put all of your team on stand-by and go inside to evolve.

After you beat the game a cave opens up at whiscash cave. You can only go in alone. You need to give items.

Some Pokemon evolve with items before you try to evolve the Pokemon that go with items like pikachu and feebas and eevee I reccomend you get 3 firestones 2 thunderstone 5 waterstones 2 sunstones 5 moonstones 12 link cables 2 kings stones 2 metal coats 1 deepseatooth 1 deepseascale 1 upgrade 4 leafstones 1 beauty scarf 1 dragon scale 1 lunar ribbon 1 sun ribbon