Invite members to your round/group

Any admin can invite new people to their round with their email address, either one by one, or as a bulk. In the "Members" tab simply click on the "Invite members" button on the top right.

How do I invite larger numbers of users to my group? 

You have two options:

1) You can use the bulk invite feature for this, which you can see when you click on the "invite people" button in your settings. Simply add all the email addresses of the people you want to invite to the round - separated by a comma.

2) Create an invite link: by clicking "Create Invite Link" you create a link next to it that you can share with anyone you would like to invite to your round