I assume you mean the Platycerium bifurcatum. They are an epiphyte (and/or lithophyte) so their natural position is on a tree or rock face. Under the nest leaves there is a rhizome or stem which branches and new plants form at the end of each branch. Each of the sections should have come apart with part of the stem and roots. It's usually quite an easy process and the way most people divide their plants when they get large. The main thing is to keep them moist/humid until they re-establish themselves.

Just earlier this year I bought 2 potted and the roots completely filled the pots. Because I wanted them mounted I had to cut away most of the roots. About 6 months later they're still going reasonably well. They'll really enjoy it when our wet season begins again (soon).

There should be roots radiating in-between the shields of the offset plants, unless you cut too close to the top portion of the plants containing mostly new growth.

What kind of soil are you using? I know regular potting soil does not spell good for this plant in cultivation for several reasons as it retains too much moisture, accumulates residual fertilizer, bad soil can also be a host for several insects, pathogens which may harm the delicate rhizomes of this fern...

Mounted, I've never faced many problems associated with my ferns and I could use some vertical spots that needed some greens without pressuring concerns because of too little space available.