1) Find the blinker
(on 4th gen, remove blinker and marker assembly, on 2k just remove side markers)

2) Find the power for the blinker ( green wire )

3) Tap a wire long enough to reach side marker ( use best judgement )
on 2k you will need to pass this wire through to the marker somehow. find a hole

4) Cut the ground on the marker (Black wire)

5) Connect the wire tapped from blinker to the ground that goes TO the marker.

DONE
The wiring should result in:

Alternate blinking with lights are on
Markers blinking in sync when lights are off
Normal marker operation when not blinking

tips:
Disconnect the wire harnesses for better reach you may also have to cut away some of the plastic wire cover.
Use electrical tape or shrink wire wrap to make things neat.