Hello,if you dont now about the portals this topic will help you to create a portal.
DIMENSIONS:
Nether:The Nether is a dimension in if you encounter ghasts(ghosts) and zombie pigmans


The End:In the strongholds,have portals destroyed if this portals are encountered and reconstructed correctly this portal transport to this dimension;in this dimension the uniques enemies are Endermans and Enderdragons

I wait you