It's the oval hole.  About 3" below the fender level is a release lever that
you depress while levering the handle of the screw-driver backwards
to pop the signal forward.

FloydR

It's a bit of a PIA, but you can remove the headlamp assembly to expose the
turn signal. the headlamp can be removed and reinstalled without seriously
messing up the aiming, and the aiming is easy if you need to do it.

As Fred said, there is a way to do this without taking the headlamps out,
but if you can't find that route, then the fall-back position is to remove
the headlamp first.