Can't find the nuget package manager in visual studio 2017?

It's not installed by default(as far as I know) you have to select It in the Visual Studio Installer manually.

First open up your Visual Studio installer (e.g., via Tools->Get Tools and Features...). Modify your currently installed product. You can find the NuGet package manager under the Individual components tab.

Can't find the nuget package manager in visual studio 2017?

As per nuget blog:

Starting with NuGet 4.0 in Visual Studio 2017, the NuGet Package Manager will be shipped as a part of Visual Studio, and newer versions will not be available for download from the VS extensions gallery. NuGet updates will be pulled in automatically along with other Visual Studio updates.

So the NuGet Package Manager extension is already built-in Visual Studio 2017, do not have to install or update it.

After install the Visual Studio 2017, you can use nuget package manager directly. Right click on the project, there is an option Manager NuGet packages..., In the Browse there filled in the openBLAS nuget package, then select the package version and install it:

Besides, you can also install the nuget package by NuGet commands directly within Visual Studio, for more detail information you can refer to the NuGet Documentation.

This worked for me:

Delete %AppData%\NuGet\Nuget.config then Restart Visual Studio

(Deleting the Nuget.config forces VS to create a new config file, this can solve many different problems depending on what was broken in your config file)