Thanks for the pictures, Patricia! Your land looks beautiful, do you ever hike up to that hill above your house? Really liking the Norfolk Island Pine, too, I wish we had warm enough winters for them where I live...
Depending on the size of those stumps, you should be able to mount your plant directly on one with no further modification. Den. loddigesii is a vigorous grower with a scrambling/vining habit so a big mount is not a bad idea. One of the nicest ones I've seen was totally covering an 18" x 30" treefern plaque and had a few hundred blooms (it smelled great!).
When I mount plants on treefern I usually put a small pad of sphagnum underneath the plant and then tie everything on with fishing line (coated wire, sturdy twine, and old pantyhose also work well). You can also tie the sphagnum on first and then the plant over top to simplify. If you water a lot or your humidity is really high you may not need the sphagnum, and once the plant has its roots into the treefern it probably won't need the sphag anymore.
This species is overall pretty forgiving to grow, though maybe a little trickier to bloom well. If your outdoor temps don't go much below 35-40 F/2-5 C you should be able to keep it outside year-round, which will help it flower better.
Generally you should water and fertilize fairly heavily during the warm months, then reduce water and eliminate fertilizer when it's cooler. Or just water and fertilize when the plant is in active growth and switch to winter care when the canes mature and leaves begin to drop. If you plan to grow this one indoors try to give it a month or two of night temps below 55 F/13 C to stimulate bud production.
Bright light a bit shy of full sun is beneficial at all times, though when it's very warm make sure air movement and moisture are high so the plant doesn't overheat. Hope it grows well for you, this is one of my favorite species!
--Nat