Creating your own AddOn - Step by Step

[Rithious]

I was looking through addons and i have yet to find what I'm looking for. I was thinking about making it myself but i don't know how to write the program. I wanted to do an all in 1 inventory. Is there someone that could help me with this, perhaps explain to me how to do this? I have gotten so use to this with all the MMO's i have played, it's actually kind of irritating not having it in Rift. Thanks