Go to devices in the Alexa app. Tap the plus sign in the top right. Select Add multi room music speakers next it will have you select a group from a list or create your own group name. I called my group that plays them all "everywhere " after you name the group a list of your echos will come up. Tap next to each one you want to put in the group or in this case all of them. Next it will take about 2 minutes to group them. When grouping complete your good to go. When you tell Alexa to play whatever just use your selected group name at the end of the command and it will play that group.