This website offers everything you need to know and have to create a private server. Several tutorials done by other members can be applied to your current version of the game. You can also develop the skills easily by reading tutorials or just by trial and error.. we all started somewhere and it doesn't take long until you start getting the hang of things. I remember doing it when I was 15!
Your best bet is to start off deciding which generation you want to recreate. Do you like 08 style Runescape? 05? 2015? Once you've decided, you can go find game versions in the download section. From there you can select already premade games (all unique with different features etc) or you can try for a basic version that you have to create yourself.