This achievement is extremely easy, below I’m going to link a couple videos that should help you.
NOTE: The video links are not my videos, I’m not taking credit for the work done here.
Here’s a quick video showing all of the locations of Ronan’s memories, there are 7 memories you need to open in order to get the achievement.
The additional link below is part 1 of a 10 part series that covers the entire game, it covers ALL achievements including “Ronan’s Story”. I recommend to anybody new to the game, to watch the series to make sure you don’t miss anything.