Staghorn ferns are epiphytes. They cling to tree trunks, rocks or whatever they happen to grab onto. They can root into decayed wood if it is porous enough, but they are satisfied to just cling to the exterior. They do not need soil. They sort of make their own soil by collecting debris that falls from the canopies of trees above. In the jungles where they live, they get all the water they need from rain. They often live in the crotches of branches because that is where they happen to land. (The epiphyte I wrote about earlier was just a palm that landed in the wrong place, but is not really an epiphyte. https://tonytomeo.wordpress.com/2017/11/15/epiphyte/ )
In home gardens, staghorn ferns are often grown on wooden plaques so that they can be moved around like potted plants. Because it does not rain much here, they need to be watered occasionally. They do not grow very fast, but eventually need to be attached to larger plaques, or divided into smaller clumps that fit onto new plaques. Alternatively, they can be grown like plants in hanging pots, but without the pots. Even if they start out in pots, they may eventually envelop and obscure their pots, and form a big rounded hanging mass that only wants water and debris from above. A small bit of fertilizer might improve their naturally light color, but too much will roast leaf margins.
My colleague Brent Green acquired this humongous and well rounded specimen from a client who wanted it removed from an olive tree that it had grown too big for. It had been there for decades. Brent gives it a banana every month or so because it likes potassium. It does not get much debris from above in Brent’s well groomed garden.