Your Didymochlaena truncatula fern is supplied in a standard nursery pot. If potting over to a bigger one, use humus rich potting compost. You could also just stand this pot in a pretty planter. Just a saucer under the pot would also suffice. Allow drainage to stand for a short time only (pour away if it lies for too long). Only water again when it's all been absorbed or it has evaporated. Do not water again if the saucer still has water lying in it. Basically, keep the soil moist.
Stand your decorative Didymochlaena truncatula fern in a warm spot out of direct sunlight - temperatures should preferably never drop to below 15 degrees Centigrade. In a cooler environment (still about 15 degrees) the plant will require less watering.

This lovely double-feathered fern (Didymochlaen truncatula) is a genuine rainforest plant that doesn't really like full sun. It does like it nice and humid so spray the leaves regularly with tepid (rain)water to keep the leaves healthy. If the surrounding air is too dry it will let you know with dried leaf edges. No need to feed this plant too much - half the dosage you will see on packaging of liquid or powder fertiliser for leafy plants.
Water less frequently in the winter. Only start again with regular watering and feeding in the spring with fertiliser for leafy plants.
 
 

The attractive fern (Didymochlaena truncatula) is a tropical rainforest plant from the Amazonian regions of South America. It grows there in the humid conditions on trees and rocks - it is what's called epiphytic.
Didymochlaena is classified under Hypodematiaceae.