Just follow 3 steps:
Install – Make sure you have Message+ before installing Group Video
Invite – via the sharing menu when in group chat
Join – with one click
You can install Call+ & Message+ App here: https://play.google.com/store/apps/details?id=com.vodafone.messaging. The apps download from the Google Play Store is free. Group Video calls uses your data allowance and is free with Wi-Fi.