ok,where can i get any power armor,i am assuming breotherhood of steel........./ thankyou

There's a set inside the lab of the Citadel. It's upstairs in the little room where the workbench is.
Crow sells some but you may have to invest in him first.
Easiest way is to find an Outcast patrol and follow them along their route until they meet their demise.

Note: You have to have Power Armor training either from Paladin Gunny at The Citadel or by completing Operation Anchorage before you can wear power armor.

Yeah Brotherhood steel, OutCast, and Enclave.

near, outside, dukov's place is often a random encounter with an enclave type. it is random but it does happen often enough to be worth checking out and it can happen more than once per game.

Wander around the D.C. ruins until you find an enclave soldier. Cap his ass and take his armor. You can't use it until you get training though.

I got my first set by looting dead BOS knights while fighting along-side them in the Arlington Library.

I've seen it come up in some of the merchant's lists as well. Not very often but it does show up from time to time.

There's some prototype medic armour in one of the utility tunnels in Olney, talks to you as well lol. Hard to get as the areas infested with deathclaws. Oh I think this is added by the Broken steel dlc and not present in the standard game, not sure though.Anyhow feed it Med-X and your good to go grunt.