Go to the Job Center to take the job. Once taken, the job marker will appear on your map. Go there.
Go to the nearest post office (see your map).
Start the delivery route.
A vehicle will appear. Open it with the U key or the 3D interaction and go to the trunk to open it.
Look at a package and use the scroll wheel to find the 3D interaction "View Delivery Address". The notification will tell you where to deliver the package.
We advise you to look at all the addresses before leaving to plan your route.
Go to the indicated location, pick up the package using the 3D interaction. Once you arrive at the delivery point, hold the TAB key to open the interaction wheel and perform the "Deliver Package" action.