VR Tourviewer for Gear VR & Oculus Go is distributed through an Oculus Release Channel.
This means it can’t be found in Oculus Home by default, but you can get access by signing up with the email address linked to your Oculus account.

Click here to sign up to get access to VR Tourviewer in the Oculus Store & Library.

After signing up you’ll receive an email from Oculus with an invitation to join the VR Tourviewer release channel. When you’ve confirmed this invitation by clicking a link in the email you’ll see VR Tourviewer in the Oculus Store in VR. Scroll all the way down to the ‘Preview Apps’. Note that sometimes it can take a few minutes after confirming the invitation before the app shows up.

You can use multiple devices with the same Oculus account/email address, you only have to sign up once then.