Some info on plans, and help needed!

I so far have most of the Dark Kingdom arc thought out. I am going to use parts from the anime, manga, and live-action series, as well as a few custom changes.

I plan to use the 'Dark Mercury' idea from the live-action series. During this part Sailor Mercury will leave the party and become an enemy (this is going temporary, and she will be able to return to the player's party). But even then, that might not be the last the players will see of Dark Mercury.

I also plan to have each character add a bonus to the group as long as they are part of the party (ones used in battles, not on the sidelines)

However, I am having trouble with RPG maker. I have no idea what I am doing. If anyone can provide a guide on how to use it, it would be appreciated.