You can evolve your Pokemon by using Candy.
What is evolving?
What do I need to evolve a Pokemon
You need to have enough candies of that Pokemon's Evolution chain. The number of candies you need can be different per Pokemon and can be found on this individual's Pokemon's page on this wiki. For example Bulbasaur.
How do I evolve my Pokemon
We're assuming that you've got enough candies for the Pokemon you want to evolve:
- Click on the Poke ball
- Go to Pokemon
- Click on the Pokemon you wish to evolve
- Click on Evolve
Evolution CP Calculation
During the evolution process, Pokemon gains additional Combat Power (CP). Each Pokemon has different multiplier by which the CP increases. It's really hard to remember all multipliers, therefore many Pokemon Go players are using Pokémon Go Evolution CP Calculator to find out what CP their Pokemon will have after the evolution.
Related: IV Calculator
I have multiple of the same Pokemon, which one do I evolve?
You should keep the Pokemon that has the highest CP (Combat Power) to evolve it to the next phase. The others can be transferred to the professor for additional candies. The reason you should evolve the Pokemon with the highest CP is that an evolution of your Pokemon will not keep the same attacks as your Pokemon. However a stronger CP of the original Pokemon will result in a stronger CP of the evolved Pokemon.