some rear hub play
 

i have i little play in my drive train.

it's not because of a loose chain. and it's not a loose cog/lockring.

i have a hed 3 rear with this http://www.hedcycling.com/wheel-acc/...te_Adapter.jpg

the part with the cog and lockring threads is moving a tiny bit forward and backwards.

how do i fix this myself. i have no idea how that part is even attached to the rest of the hub. i know how to remove the axle and cones, but that's it.

Thats a surly fixxer. It replaces the casette hub on the hub. I had one, worked great but did get loose once. Remove axle, and use 10mm hex wrench to tighten.
Read about ithere.

i'm not seeing anywhere i can use a 10mm hex key

Aww man. I thought this thread was going to be about a play starring a hub.

Remove the axle. Insert hex key where the axle was.

Just as you would to remove a freehub.