How to Mod?

Can someone please help me on how to mod nba 2k11...like how to mod the accessories, tattos and etc....
please post and application i need and the links

heres the mod tool
viewtopic.php?f=136&t=75639

and poke around this forum for tutorials
viewforum.php?f=138

and if you have no idea what you are doing
viewtopic.php?f=132&t=77126

well I already know how to do these but i want to know how I can create my own...
like which programs/softwares will I need to use inorder to create my own accessories (ex: dwight howard sleeve) and etc....
Ty for the Help

photoshop? gimp? paint?

we dont necessarily create anything new, we just modify what already exists

o how?