Google photos is not integrated in Tribu, we have done better: we have integrated Tribu in google photos.
This way you can take advantage of all the power of Google to choose your photos, and then import them into Tribu directly from google photos

How to do it?

Select the photos you want to share
Click on "share".
You land in the Tribu application and can select the Tribu(s) you want to import your photos into

The photos are then imported directly into your Tribu-families, and you return to Google photos.

So after the import, you have to leave the Google photos application to go to the Tribu application

It's as simple as that