Pro Tools | First can be installed on up to three computers at a time.

To install Pro Tools First on additional computers, download and run the installer from your Avid account on the new system. Once the installation is complete, open the iLok License Manager program and sign in to your iLok account. You will see your Pro Tools First license listed here, which you can then drag onto your computer in the left sidebar under 'Local' to license the new computer.

What if I've used all 3 activations?

You can install Pro Tools | First on additional computers by deactivating previous ones. You can only do this from the computer you no longer wish to use Pro Tools First with. You need to deactivate the license using iLok License Manager as per the screenshot below.