How do I resize the band?

If it's the one with individual links you can use a jewelers screw driver to remove a few. Or go to a jeweler/watch shop and have them do it. There might be a small charge. I've had to this with watch bands in the past so I bought a few of the tiny, jewelers screwdrivers.

Only the Link bands can be adjusted. Look on the underside of the band. You'll notice that some of the links have a "button" on them that looks very similar to the band release button on the watch itself.

Search Apple Watch support site for detailed instructions.

Rysz is right, some of the links can be removed by pressing the button on the inside of them. If you search on youtube you can find videos of people showing the process. It's a pretty simple one once you realize the trick to it. Hope this helps.

Many such bands do use tiny screws that require a jewelers screwdriver. Apparently that one doesn't. And I'm certain the poster would have been able to determine whether it did or not. Since my other suggestion was to go to a jeweler I don't think any harm would have been done. However advice from those who actually have the band is obviously more appropriate.

No violation. And if you don't need a screwdriver, even easier to do.

If the OP took your advice and attempted to use a screwdriver, it would have resulted in damages and a voided warranty.

Please always double-check your answers before posting. Thanks.

If you don't feel comfortable doing the adjustments yourself, take it to an Apple Store and let them do it.

Enjoy!