Insert the transfer paper into the printer (most arts and craft stores sell this transfer paper).
Launch the document you want to print, click "File," "Print," and select the printer you want to print. Click "OK," and the image prints onto the iron-on paper.
Cut away the unwanted paper around the image you want to apply to the T-shirt.
Spread out the T-shirt on an ironing board or other flat surface. Power on the iron and turn it down to its lowest level (anything higher may burn the material).
Press down on the iron-on paper. The heat from the iron adheres the paper to the shirt. Run over the entire image to make sure it bonds to the shirt. When done, allow the shirt to cool and dry before wearing it.