Find a heavy spruce tree that stands out near water. Cut a low limb free of branches leaving only the clean brach sticking out. Nail your fence staple through the ring onto the tree. Use either a piece of heavy string to tie the trap to the tree branch, leaving the set trap at the end of the branch. You can use a half twist of light wire to do the same thing. Place a wing or attractant above and out of reach, so he has to stand on the foothold to get near the wing. Put some Gusto on the wing and remove the wing at the end of the season (bears) leaving the trap unset hanging off the branch. You can use bait under the branch and trap if you want. Lure on the wing will do the trick by itself if you are in good Marten country. I use this method a lot. Sometimes I use a box and this set right next to the box, double catches are common up here in Alaska.
This is just one way, there are others. You can make these or use a running pole wired/nailed to the side of the big spruce tree to keep the snow off and trap working. Bait I like is duck carcasses, salmon heads, beaver, muskrats, duck and goose heads, wings with lure, fur with lure. Some guys like cd's on fishing line, some even add a swivel to the line and cd's to help it spin in the wind. Yellow, Pink and Red Surveyor's ribbon works okay, but is easy for humans to spot. You can even use a bracket and put them on the side of the tree and nail some bait above the trap. Lot's of methods, just have to find one that works for you and is legal in your area.
You can use a cubby made from stuff around the tree, you can use a box with the foothold inside, you can use double ended boxes with a trap at each end, lot's of ways to catch marten with footholds. Keep them off the ground and let them swing free in the air to keep the other animals and mice off of them is a must. Don't put sets on the ground, something will eat your marten for sure. Use #0 longsprings, #1 coil or longsprings, up to a #1 1/2 coil or longsprings at most. I use #0's and #1's, my 1 1/2 are too big for my liking. Good luck!