There is a link on the homepage here:
https://bitbucket.org/mrshrinkray/chello/overview
To the zip file containing examples etc.
https://bitbucket.org/mrshrinkray/chello/get/d6eef8794afd.zip
Download it, unzip the file, Add the Chello.Core project to the same level as your existing projects.
Right-click your solution and choose add existing project, select the Chello.Core.csproj.
In the project that uses Chello, add your appsettings for authkey and token:
<add key="AuthKey" value="YourAuthKey" />
<add key="AuthToken" value="YourAuthToken" />
Unfortunately I don't think there is a nugget package.