Eevee has a total of eight evolutions available in Pokémon Go. All are unique, and Eevee's evolution in those Pokémon varies. For example, in the original games, you would typically use a specific stone. But none of those in Pokémon Go. So the developers had to get creative with the process, and if you're looking to evolve an Eevee into Glaceon, it's a little easier than the other evolutions. This guide explains how to evolve an Eevee into Glaceon.
In order for an Eevee to evolve into Glaceon, all you need to do is make sure your avatar is on the Pokéstop that has a Glacial module assigned to it, then evolve it. This is all there is to it. Any Eevee you evolve while within range of a Pokéstop while that decoy module is active will become a Glaceon. The problem boils down to locating a glacial module.
Sometimes you can receive them as exclusive rewards for completing Special Research Tickets or Timed Research Activities. Besides that, you can also buy them directly from the Pokémon Go store for 200 Pokécoins.
There is an alternative to this method. You can instead name your Eevee Rea and then evolve it without using an ice form. This process causes Eevee to evolve into Glaceon, but you can only do it once. Each Eevee evolution has a name trick method where if you change that Eevee's name with the specific choice, it becomes that evolution. The downside is that you can only use it once, so you want to use it wisely.
Once you have a Glaceon, you can expect to use it in PvE battles, against other PvP players or Team Rocket members.