All the info u need on creating custom content, including a lot of tutorials, can be found at Mod The Sims (
link). However, u need to be really good at 3D modelling and have the right programs for it if u want to create stuff from scratch of modify the shape of existing objects. If u just want to do recolors, then u need a good graphics editor like Photoshop. u also need a program called SimPE to pas aan the package files. If u go over to Mod The Sims and have a look there, it tells u all u need to know. But it's not easy - I had a go at just modifying the size of some hoop earrings to make them bigger, and it took days to get them working right!!
