To join a Shared Wallet with another Bitcoin.com Wallet app user, you will need to either scan the QR invite code, or the creator of the Shared Wallet will have to send you an invite code.
Step-by-step instructions to join a Shared Wallet by scanning a QR Code
Tap on "Scan" and scan the QR code with your phone camera.
Your wallet should automatically take you to the "Join shared wallet" page.
Enter your "username"; this will be your co-payer name.
Tap on "Join Wallet."
Be sure you have cloud backup enabled. If not, you’ll need to write down the backup phrase for your new shared wallet and keep it safe.
If you lose the phrase, you’ll lose access to your shared wallet in the event you can’t access your phone.
Please see an instructional video here: