I need help to set the timing on 1999 ford expedition 5.4l.

If it's valve timing you are referring to, follow these steps.

Orient the crank sprocket with the mark at the six o'clock position. Fold both chains in half, with the two copper links on one end, and the single copper link on the other end. (If there are no marks visible, you can make your own using paint, or other suitable marker that won't rub off)

Install the timing chain guides. Begin by setting up passenger side bank cam, with the single copper link lined up with the mark on the crank sprocket at the six o'clock position, on the INNER gear (the one closest to the engine). While holding the cam with vise grips, route the chain with the two copper links lining it up to the mark on the cam sprocket (sprocket should be at around the 11 o'clock position). Install the right side timing chain tensioner, and torque to two 10mm bolts to spec.

Repeat above outlined procedure for the driver side bank cam (sprocket on this bank should be at around the one o'clock position).