In order to play an online match, you need to create a Ubisoft Connect account or log into said UC account if you already have one, and then go into Network Game. From there, you can create an Online Game, or join one. Once the Online game starts, you MUST play through from start to finish, beating the stage boss, for this achievement to unlock.
In regards to Ubisoft Connect, you can download the app for Xbox One.
Good hunting!