You will want to lap the flashing on the door jambs.
How to install garage door flashing.
How to install z flashing on an exterior door.
The weather resistive barrier wrb material should be installed over the top of the door head flashing material.
An important part of installing new doors and windows on your home is properly sealing them.
Install each additional small siding piece in the gap between the garage door and the corner in the same way you installed the first piece.
Next comes another layer of building wrap installed like the first layer.
Install the trim just under the drip cap.
See attachment i see siding installed tightly on top of the flashing.
If siding is already installed on the exterior of the house remove the section above the door so that you can install the flashing directly against the sheathing.
Apply a bead of caulk to the felt and set the window in the caulk.
A self adhered head flashing strip should be installed across the top of the doorway and over the drip cap vertical leg.
The flashing will need to overlap the edges of the sill and go down past it by at least one inch.
Follow the directions provided by the manufacturer for installing in in the rough opening of the door.
You will want to use the self stick flash on the side jambs next.
Gaps around the window or door can create drafts which.
The head flashing strip should extend a 6 inch minimum over the top of the side jamb flashing material.
When installing the flashing the longer edge goes against the wall of the house the center section rests on top of the casing and the short edge goes over the front of the casing.