You can download the IDP metadata, upload it into the appropriate service provider Setup fields, and then come back to the admin console and click Next.
This is Google SAML - which is idfferent than the tradistional Google Oauth.
Note that using Oauth has a simpler setup and can allow additional email domains.
Using Google's SAML may restrict users
For this setup we'll use the instructions posted by google at
When choosing Entity ID/Single Sign On URL vs IDP Metadata file, we'll need to choose to download the file from Google.