You can use a credit card (or cut up one.. use a plastic fake card from the mail, a good playing card, or a plastic drywall spacer are all possibilities.) And try to push the bubbles.. if one direction doesn't work, try another direction. If the screen protector is already set - you'll need to either live with it, or try to remove & replace it without ruining it.
After drying for a couple of days, it may be hard to do this without ruining it.
The air bubbles are pretty much stuck if everything underneath is dry. You have to find a way to get some kind of lubricant ( water, oil, still-pliable glue) between your screen and the plastic protector.
Usually, water is most commonly used since it won't damage anything involved.
(*Just a couple 3-4 drops at most.. we don't want to short the phone! *)
If you are ready to try, pull up the plastic from one corner, and work it diagonally across. Leave the opposite corner connected once you are free of air bubbles. Put one or two drops of distilled water (or what you have .. distilled won't have any residue when dry) on the screen, and use a free finger to wipe it all over, fairly evenly, but not perfect.
Now, slowly - using your card-type thing, start from the "good" corner, and work a little at a time out from that corner in each direction. Just a millimeter or so in each direction, and keep the other corner of the screen protector a little taut pulled away.
If you see one bubble form, pull the plastic back up.. just that one mm , and reposition/reapply it. If the screen gets dry, add another drop of water, one at a time -spreading it out.
If you are very patient, take your time, and don't let the screen protector capture any air bubbles, then you have none to press out later.
If you notice one or two tiny imperfections.. ( humans do that ) then take your card and work the plastic while it is still a little moist underneath. After you are satisfied, let the phone sit overnight - OFF- to allow the screen to set.
Keeping the battery out for this whole process will avoid any electricity + water problems, and keeping it off will help you while applying - less glare; and while drying - no heat from phone.
If your vendor offers a guaranty, then ask them to replace your damaged screen protector if you need to.