For best results you will want to use a product to pretreat your fabric before printing. There are several to choose from, Bubble Jet Set is the only one I can think of off the top of my head. You should be able to find it at Joann's and other fabric stores.
There are great instructions here:
http://www.theartfulcrafter.com/bubble-jet.html
and Caryl Bryer Fallert uses it and has a page full of information here:
http://www.bryerpatch.com/faq/bjs_q&a_page.htm