If your watch strap is held on by standard spring bars, then you need to remove them with a spring bar tool or a micro screwdriver.
Here is a link to short video which describes the watch strap removal and replacement process in excellent detail:
Just use your mouse to click on the link, which is the underlined and highlighted text just above. This will open a new web browser page automatically for you and allow you to view the information and items at the website indicated.
I hope that was helpful to you, good luck.
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