You do not need to register or log-in to reddit get this achievement (or at least I didn't have to). From the home screen, press
Change Subreddit and click the
Search Subreddits button. Type
xboxone into the search bar and click search. You should find
/r/XboxOne - The home of everything Xbox One on Reddit as the top result. Click this and choose any of the filters - I chose
hot. This should be enough for you to earn your achievement!