Sorry should have been rein, not rain. Wrong word! My bad. When you can pick where you're going is what inmeant. I looked it up on the wiki

Acquisition

Prerequisite: Mass Effect 3: From Ashes
Prerequisite: Priority: The Citadel I
This mission is acquired by downloading the Mass Effect 3: From Ashes DLC and accessing your personal terminal. It is immediately available upon gaining free rein of destinations in the Normandy SR-2 after departing the Citadel.

Priority Mission: Eden Prime