Welcome to Shopify Community. My name is Olivia and I work here.
I am sure I can help you figure this out today. We can get this to work one of two ways: a) either with custom code, or more likely b) through the theme's settings. To make sure I don't miss or misunderstand what you need, is it possible for you to grab me a screenshot of the button you are referring to?
Otherwise, I assume you are referring to this button in the Narrative theme slideshow:
If yes, once you are here from the Shopify Admin > Online Store > Themes > Narrative > Customize Theme > Slideshow > Content section you can copy/paste the exact URL you would like to re direct the button. You can even search for the specific collection under button link if you prefer as such:
Does this help answer your question? Please let me know.
I'll be on standby waiting to help,