This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
From: Mark Hickey <email@example.com>
Remove the old decals completely (including any residue). There
shouldn't be any clear coat on top of the decals (hey, it's a ti
bike). I'd suggest cleaning the tube with acetone or other solvent to
make sure it's clean.
Peel the heavy paper backing (I'll bet it's green) off the decal.
Place the decal VERY CAREFULLY in place, starting with the top making
VERY CAREFULLY rub down the decal so it makes contact with the frame
(you'll be able to see where this is happening).
Once the decal is placed on the frame, vigorously rub the decal with a
clean rag to create some heat (start slowly to keep from wrinkling the
When you're done, lightly "squeegee" over the decal with the edge of a
credit card or something similar. You'll see the decal release from
the backing as this happens.
If you end up with an air bubble, you can usually pierce the decal and
squeeze the air out (with the backing still in place, or "reapplied".
It takes a few days for the decals to reach full strength (they dry
from the outside in). Be careful with 'em during that period.