Getting VS Web SDK up and running

I need to get the SDK for web going.

I'm trying to follow along with the instructions here: https://developers.vertigisstudio.com/docs/web/sdk-overview#getting-started

and when I try step 3, I'm getting the following:

PS C:\Temp\SDKtest\testapp> npm start

> vertigis-studio-web-project@1.0.0 start
> vertigis-web-sdk start

'vertigis-web-sdk' is not recognized as an internal or external command,
operable program or batch file.

what am I doing wrong?