GitHub Enterprise and Nuget Package Sources

I’m trying to setup a package source in Visual Studio 2019, I have tried several times but repeatedly get a 401 Unauthorized response when I then try to browse the packages.

When I use a browser to access our GitHub repos I often get prompted to authenticate with my company’s credentials but there seems to be no option for specifying this with Nuget.

So technically I have two sets of credentials, the first is my own GitHub userid/password and the other is my company’s (who own the Github enterprise instance) userid/password.

How can I setup a package source in Visual Studio that enables me to see our packages?