This achievement is as easy as it sounds, all you have to is play one round on all of the maps. It does not have to be a full round if you join in on the last few minutes it still counts. Just keep track of the maps you have played and you can use the server browser to find the maps you still need.
Go to server browser
Hit Y
Go down to maps
Select the maps you still need
The maps that you need for the achievement are:
Brusilov Keep
Albion
Lupkow Pass
Galicia
Tsaritsyn
Volga River
You don't have to win just finish the round.
One side note if you use server browser sometimes the maps will rotate as you're loading in so be prepared for this.
Courtesy of Or1g1nalS1nn3r you can use the codex to see what maps you have won in, and this will help narrow down what maps you might have missed.