iMessage on Beeper - How to enable Text Message Forwarding on your iPhone?
Learn how to send and receive texts (SMS) from your iPhone into Beeper, unlocking even more messaging capabilities.
TL;DR
To receive SMS/Texts on Beeper → Go to your iPhone Settings → Messages → Text Message Forwarding → Then enable the mac with name Beeper Mac
iMessage on Beeper - How to enable Text Message Forwarding on your iPhone?
Enabling Text Message Forward for iMessage on Beeper will let you send and receive messages on your SMS chats. For this, and as advised while you're connecting iMessage to Beeper you have to do the following:
On your iPhone, go to Settings > Messages > Text Message Forwarding, and make sure Beeper (Mac) is enable. If it's nor, you can enable it from here.

On your Beeper Desktop, you can confirm this has take effect by going to the iMessage view. Go to Beeper Desktop > Gear icon > Chat Networks > iMessage. Text Forwarding must be enabled; it should look like this.

Note
It is important that you verify that you're able to receive both iMessages and SMS messages on your Messages app before setup. In the event that you're unable to, please reach out to Apple or your Wireless Carrier for further assistance.