In most code bases, skills are usually hard coded into a skill table of some sort. Although I am not familiar with dbx, I would assume it is contained within a file called skills.c or something similar. Although you can just add-in what you want, there is typically much more involved, thus requiring a base knowledge of C, and an understanding of the entire structure of the application.
Not trying to discount your question, but even if someone provided step by step instructions, you might need To Learn more than you think.
If you're looking to create a series of similar skills, you'll find it easy, except for syntax issues. On the other hand, if you want a wide variety, you are going to have to study–a lot. Even more than you think you will. Probably even more still. Start with a good website (like Zeno linked) or a basic programming book in whatever language your mud uses.
Put more bluntly: go learn how to do it (links have been provided as good first steps) and quit asking people to do all the heavy lifting for you. Nobody here has any reason to invest time into your MUD, and so far you have even managed to very firmly give us all the impression that you're too lazy to learn how on your own. We can answer specific questions, but saying "help me do it without learning how" really means "do it for me," and that just isn't going to happen.
Also, do realize that people might be slightly more willing to invest time into providing more complete and concrete answers to your questions if you didn't type like a low-GPA 13 year old.