You can use GlotDojo Premium Add-on on maximum 3 different devices at once.
Use Premium Add-on on a new device
Sign in with the account that you used to purchase Premium Add-on (Chinese/Japanese)
Open Settings => select Dictionary Add-ons (1)
Step 3 - Select the language you have purchased Premium Add-on for (2) => Click Restore Purchase (3) => Done
After restoring purchase successfully, download Advanced Dictionary (4) to be able to look up words with the Premium Add-on on your new device.
(Note: You need to download Chinese - English or Japanese - English dictionary before downloading advanced dictionaries in other languages.)
2nd way to "restore purchases"
Open Dropdown => Select Account tab => Click Restore Purchase (3) => Done
Then, just go to Settings and download Chinese - English or Japanese - English dictionary and the advanced dictionaries in your language (if available) to start looking up words on web pages & video subtitles with GlotDojo Premium Add-on.
To see and manage all the devices you are using Premium Add-on on, go to Settings => your Avatar => Subcriptions