Edit: Comments indicate you only need to wait a year after first playing the game. So you can risk not creating a HR account, or make one to be safe.The description is fairly self explanatory, you must have a Paladins ACCOUNT. As far as I know, this is different than simply playing the game for a year.
You'll need to go the Hi-Rez's website and link your Xbox and Hi-Rez accounts, which you can do here:
https://www.hirezstudios.com/linkFollow those steps and come back a year later to earn the achievement.
As I do not have this achievement, if someone who does can add any further detail, if there is any, it's appreciated.