Xamarin and MongoDB and Couchbase lite - error adding nuget

I am trying to add a MongoDB nuget and also a Couchbase Lite nuget to my project. I am trying via adding it to the Xamarin.Forms project and also trying to create a PCL as well.

I am unable to add the nugets in and am getting the following message.
"You are trying to install this package into a project that targets 'portable-net45+win+wp80+MonoAndroid10+xamarinios10+MonoTouch10', but the package does not contain any assembly references or content files that are compatible with that framework. For more information, contact the package author."