Our very first spectacles (Black, Coral, Teal) are one-size-fits-most.
If your Spectacles feel a little loose, try tightening the screws. You’ll need a very fine slotted or flathead screwdriver (anywhere between 1.5mm - 2.0mm). You can find these in most glasses repair kits.
If you need adjust the way your Spectacles fit, take them to a qualified optician. But be sure to tell them not to apply heat or water anywhere near the front of the frame where the electronics live.