Please note: Due to new Facebook updates, only Facebook pages with 2,000 likes or more can create custom tabs to embed virtual tours.
Using Page Tabs
You can add custom Page tabs via Facebook. These custom Page tabs load content from your web server using an iframe. Page tabs will only be displayed in the web UI. Mobile custom tabs are not supported at this time.
“To ensure tabs lead to high-quality, accurate content, the Page Tabs feature is only available to Pages with 2000 or more followers, or pages managed by whitelisted apps.”
Read more at Facebook for Developers
As you can see the tab is by default named “Welcome”. You can now go to “Setting → Edit Page”, find the tab “welcome” and click on “Settings” beside the tab to edit the tab name.
Note: Don’t forget to press “Save”!