when you do stfs you get salvage which i think they have now renamed to datachips.
basically if you get 20 of those you can trade them into the requisition officer and he will give you a token for a certain piece of equipment. you then use that token on the relevant vendor behind him.
you can also get rare chips that will by you one piece straight away (so no need to collect 20 pieces). again use the requisition officer and just buy the token you want. then trade it in for the piece of equipment you want.
some of the items are under the special reserve tab. these are the sets for ground and space. these require 30 normal chips or one very special tech chip.
this is all for the X gear, mark XI for example is more expensive in terms of the number of pieces you need. its confusing at first but just play around with it and it should get clearer.
Take it from the Availabe Missions List, then go to Personnel in ESD or Quo'Nos. Talk to them. Then go to Completed mission List and Award is available to get. I did that yesterday, and was also confused until I checked my completed mission list, and found the STF Req in there.
I was able to complete the mission on KDF side, because I got a pop-up from D'vek which gave me a chance to speak with him. Or that is what seemed to happen anyway.
On the Fed side, After taking the STF Equipment mission from the "Available" list, I had no such pop-up window. I was also unable to engage him by "Speaking with the Re Officer"... In fact I spoke with all 3 and the mission remains incomplete in my mission list.