Authy supports Multi-devices, so you can share your tokens across all of your Authy devices. When you link a device to your account it will immediately synchronize all of your tokens.
Let's assume that you have two devices, A and B, where A has Authy installed already. Both devices can be anything from an iPad, iPhone, Android Smartphone, Android Tablet, etc.
1. Make sure Authy is installed on device A. Go to Settings > Account Info and take note of your Authy cellphone number and country code e.g. (+1) 111 - 111 - 1111.
2. Make sure Authy is not installed on device B. If it is, uninstall it and re-install it again. Open Authy and enter the same country code and cellphone number on device A.
3. You will be prompted to choose between SMS, Phone Call, and an Existing Device (see screenshot below).
(Your actual screen might look a bit different)
4. Click on Use Existing Device.
5. Now open device A and open the Authy app. You will see a screen that is requesting permission to add a new device to your account.
6. Approve the new device.
7. Your tokens will sync shortly: You have successfully linked a new device to your Authy account.
To make sure the process works go to Settings > Devices. You should be able to see a new device.