CORS Access

I'm trying to access a web api  in an appian cloud from an angular app, but the cors policy is not letting me access. I'm getting the following error 

access to XMLHttpRequest at 'xxer.appiantrial.com/.../YtKYs0w' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

Help!

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