Help with API

I have never used an API.  How do I assign a value to a field with an url API?  I want the user to click a link of dashboard and the API to assign the value to the first field on the form from the link.

This is the url to the form that I  want to assign the value for field Managing Company.

I know the API gets added to the url, but not sure how to format it.  This is the url to the form: https://jsupor.quickbase.com/db/bn9gef6we?a=nwr.  What would be the url if I want the form to open with Managing Company assigned "Supor Sarens, LLC."?

Any help is greatly appreciated.