[Question] A general question on ROM hacking

I'm starting a project, making a pokemon game, and I have downloaded RPG maker XP and the latest pokemon essentials version, 20.1. I have been having trouble figuring out what to do. The youtube tutorial I have just kind of has the guy doing something I can't see and then magically having a pokemon template. If someone could help me out with getting started that would be great as I want to do this, and it would suck if I couldn't because I couldn't get this to work.

Our you trying to just open it? To open Essentials, go to the folder in which you have it installed, and click on the "Game" program that is a "RPGXP Project" type. That should open up the demo world in RPG Maker (if you have RPG Maker on steam it will attempt to log into steam if you are not logged in.)
From there, I would look at some of the events in the demo (like the player's mom, the example gym etc.) to kind of get the feel of how the system works. You should also check out the Pokemon Essentials Wiki as well as Thundaga's youtube tutorial (which is on an older version of Essentials but most of the basics still apply). These are the three best resources to help you get started making a Pokemon fangame.