According to a report from Wristly Apple Watch band ownership is increasing, going from about 1.4 bands per user to nearly two bands per user. If you’re going to own multiple Apple Watch bands, you should know how to change ‘em.
Before you change your band, place your Apple Watch face down over a clean surface like a lint-free, micro-fiber cloth or soft, padded mat. If you have a Link Bracelet, press the quick release button on a link to separate the band into two pieces. If the band doesn't slide out, press the band release button again and make sure that you hold it down.
Hold down the band release button, then slide the band across to remove it. Make sure the text on the band is facing you, then slide the new band in until you feel and hear a click.
Never force the band into the slot. If you don't feel or hear a click, slide the band to the left, then to the right. If the band is installed properly, it won’t freely slide until you hold down the band release button. If the band still doesn’t lock, center the band, and push it into place. Then carefully wiggle the band up and down. Don't wear your Apple Watch if the band is sliding.