CORS

There is a cors error with my api and when I try to use it on another website it works

 Access to fetch at '{MY API}' from origin {MY WEBSITE}' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

how do I fix this ??