upgrading Visual Studio 2017 to use .NET Core 2.0

I undertook the following steps and I cannot say if these had to happen in this order exactly.

1. I downloaded and installed .NET Core 2.0.
2. I clicked on the flag in Visual Studio 2017 Professional and then clicked something-er-other to prep an update, though this itself did not update anything.
3. I closed Visual Studio 2017 Professional.
4. I typed "Visual Studio Installer" at the start menu to spin up Visual Studio Installer and I let that app do its thing.