If you're already on the search for secrets, force echoes, exploration completion etc. this achievement should come naturally while playing the game.
If you're going for the achievement above you will unlock Echo Location
Still missing force echoes that you cannot seem to find?https://segmentnext.com/2019/11/20/star-wars-jedi-fallen-ord...
this guide will help you locate the remaining ones.
If you're stuck on getting a force echo without remembering which ones you have retrieved already I recommend going to the databank. Anything missing there could be a force echo you didn't find during your search. Don't be fooled by seeing 100% on areas. I've found some force echoes in dathomir to be exact where it said the area was fully explored but for some reason there was still a force echo lying on a platform! I am not sure if this happens in other planets/areas, but just to be sure, check!