You can pick up a USPS package before delivery if the package is at your local post office and has not left for delivery.
To pick up your package before delivery just be sure to bring ID to prove who you are.
If the package is still at the USPS local post office that makes deliveries in your area you could pick it up.
However if the package is already in the USPS vehicle for delivery then you'll have to wait until it gets delivered to your address.
Most USPS packages are loaded and ready for delivery by 8:00 AM or sooner and once they are out for delivery you can't get the package until it arrives at your door or mailbox.
It's easiest to just wait until the package gets delivered to your address as that is what the USPS mail carriers job is for.
They will get around to your address and deliver the package and if it says out for delivery then you'll get the package that day.
Some USPS packages arrive by 9:30 AM and some arrive after 12:00 PM depending on where you are on the mail carriers route.