Like most all mosses, Java Moss is an easy to grow, begginer level plant that can grow in nearly every aquarium. It does best when attached to a surface to grow on such as a rock or driftwood. This product comes un-attached and in long strands which promotes health while growing. If you intend to grow this plant out, then it may be best to leave it free-floating and long, but if you intend to use this plant in an aestetic way, it is best to cut it extreemly short and use superglue to attach it to a surface. or to use fishing line to tie it onto the surface until it attaches to it itself. The only downside to the fishing line method is that the fishing line must be removed after the moss has attached itslef where the superglue dosn't need to be removed.
If you wish to learn more, this link is a video that goes deeper into Java moss. It is by Cory form Aquarium Co-op.