If you already have your groups on another device or in the web client, the best way to start with the Android client is to go to your previous client > Config > Backup and Restore on your phone so you can keep all your previous messages. You can also link both devices using the multi-device options. If you don’t care about keeping the history of your previous messages, you could simply link the devices via the multi-device feature, and you’ll get all your groups synced. Enjoy!