Once you have chosen to start a loop and you have continued past the first pop-up window, you will come to the leader panel. Here you will see Add + just below the headline Participants. When you click Add + a new pop-up window will appear where you write the names of each participant or the name of a group (if you have created groups for your organization in Loops). If you write the name of a group, all the participants will appear at once. If you have a new participant who has not yet got a Loops account, you can invite that participant via email and s/he will create an account going into the loop.