Go to Google groups and select 'My Groups':

 

Find your group in the list, then click 'Manage':

The Google groups created for Solvay ONE are named "$AODocs Solvay ONE [Your Solvay ONE space name]"

 

Select 'Direct add members' on the left:

 

Than add the mail addresses and a welcome message for the new members.

  • The Google groups for Solvay ONE are named as follow: $AODocs Solvay ONE [Your Solvay ONE space name]   
  • If the will be only used for web contribution, you should avoid setting up mail subscription.