Remove rocks holding the edges to allow liner to conform to the edges of the hole. Smooth out wrinkles but do not pull too tightly. You can walk on the liner if you remove your shoes. Place rocks around the edge to securely hold the liner in place. Install pump and filter, if desired.
Many smaller pumps have a built-in filter.
For larger pools, a separate pump and filter may be necessary. Make sure the filter and pump are adequate for the volume of water in your pond. Pumps not only add interest, but are important in adding oxygen to the water. If you want a fountain or waterfall in your pond, you will need a pump to circulate the water. Let the pond sit for a few days before adding fish and plants.