The best way is to request a DISign directly from the DISigner, especially if you want it personalized or altered. Then you can save it onto your own computer (either directly from the thread or from the DISigner's photobucket or shared file) then print it out at home using T-shirt transfer paper (IMHO the best is obtained via mail order from Amy who posts here as M.I.C.K.E.Y) and iron it onto your shirt. There are a couple of threads with more detailed instructions on how to do this.
I hope this helps
Hugs
Joanne