On fallout 3 when do you get the suit?

Answer 1

The Citadel. Speak with Elder Lyons first to obtain clearance. Speak with Paladin Gunny. You can find him walking around the training area in the Citadel.
In the main quest line you will go into a sewer and come out in-front of somewhere called the citadel,Ask paladin gunny [usually in the courtyard] if he could train you,He will tell you he needs elder Lyons permission. Seek out elder Lyons and ask permission from him,once he has gave you permission, return to gunny and ask for power armour training.

Answer 2

there are a bunch of suits in fallout 3 so be more specific