This achievement is a piece of cake.
In order to unlock this you first need to pick your very own Warframe
(Excalibur, Loki or Mag) after the tutorial. Be aware that once you pick one it might take some time to get another one, that is if you don't want to pay any real money. Deleting any save-files won't help since it's tied to your profile. So make a wise choice.
The max rank you get to is 30
but you only need to aquire RANK 2
so you will get this achievement quite soon in the beginning by simply killing enemies with either your primary, secondary or sword weapon and completing a few missions. Don't worry!
The achievement should/will pop during the mission right away.