API on website?

I have a question if someone can explain to me how to add my fortnite shop api to my website. I have my website already with a kit Dsignt but I have no plan how to insert this api

You should reveal more details.

Has the API been developed by you? If so, with what? If the API comes from someone else, look at the developer side, there's usually a documentation. Here, for example. For a Fortnite API: https://fortniteapi.com/docs/open/1.
What is your website based on (web server, used building set, …)? Do you even have the opportunity to write your own scripts? Insert?