Figured it out. I wasn't able to add the winforms class library to the project references because my project was targeting .NET version 4.0. It will add the core OxyPlot library, but it will throw an error when you try to reference the winforms DLL.
You have to manually set the project's targeted framework to version 4.5. You do this by manually editing the project file and adding <TargetFrameworkVersion>v4.5</TargetFrameworkVersion> to the globals section.
Once you've done this, you'll actually be able to reference all of the required class libraries and the toolbox will now be usable.
You have to manually set the project's targeted framework to version 4.5. You do this by manually editing the project file and adding <TargetFrameworkVersion>v4.5</TargetFrameworkVersion> to the globals section.
Once you've done this, you'll actually be able to reference all of the required class libraries and the toolbox will now be usable.