Hello! I'm looking for some help with getting my photo slider to stretch to fill the screen width.
The easiest way (for me at least) is to use one of slider generators e.g. https://wowslider.com or https://cssslider.com. There are quite few others but it becomes personal choice and other members here will have suggestions too.

You can code a full browser width slider, but with generators there are lots styles and effects that would otherwise take some hours to perfect. Some of the generators do have a watermark unless you take the paid version, but most you can test for free.