get a stencil. my favorite place to get them is http://kittybuttons.com/wordpress/
i highly suggest you print out your stencil on cardstock, so you can reuse it&&it wont be terribly filmsy&&difficult to work with.

cut your stencil.if you're painting onto light fabric with darker paint,cut out the black parts.
if you're painting onto dark fabric with lighter paint,cut out the white parts.be patient with this!
if you need to cut out an island [[the white part of an "o" for example]] cut it out&&set it aside

tape your stencil onto your tshirt using masking tape.tape the islands where they need to be by rolling the tape.

slide some poster board in the shirt to prevent the paint from soaking through anything or getting on anything it shouldn't.using a paper towel,dab the paint where it should be.wait about an hour for it to dry.

after the paint is dry, iron it for the instructed time on the bottle.if their isn't an instruced time,iron your shirt with a paper towel between the shirt&&iron for a few minutes.

handwash it in woolite insie out. [[you don't need to do this everytime you wash your shirt, just the first time.]] i'm not sure if you have to do this with fabric paints, but i only had acrylic paints around, so i handwashed it.
let it dry.

yay its done! make sure that when you throw it in the washer, you wash it inside out.