Go to the Google Marketplace. In order to authorize Signitic, you have to click on "Domain install". Careful: if the button "installation for the whole domain" is grayed out , it means that your Google account is not Administrator G Suite. You will have to ask to your G Suite administrator to do this step for you.
Accept the different authorizations: The requested authorizations allow you to retrieve the list of your users and their attributes as well as to be able to update the signature for each of your collaborators!
This step is very important ! Complete the configuration by clicking the Signitic button in your Google task bar which is now available. Google will ask you to login again. Please use the same admin email.
Update your signatures via the button available on the Dashboard "Update my signatures".
Update your Gmail to discover your new signature!