you can purchase (made for printing) fabric printer sheets at some quilt shops, joannes, hobby lobby, ect...
or you can purchase PFD fabric (prepared for dyeing)
or you can prepare your own.
you need an ink jet printer- a laser printer gets too hot...does not work well
you can purchase a liquid stuff called bubble jet set- follow the instructions on what ever product you try.
the ink needs to (cure) so set pics aside to dry for a few hours after printing- then heat set---
some products work better than others...there are many tutorials...check them out! :)