How do I customize PM? (Stages,Character's Costumes,ect.)

[iAdversiity]

I want to change the stages and add new costumes for the charater's,but I don't know how.Can someone provide a link or walk me through it?
Thanksss <3

 

[ECHOnce]

Check the PM Customized Content forums. Also, Theytah has quite a few tutorials for helping those new to modding for PM.

 

[standardtoaster]

moved to custom content