Just like any other Magento extension, simply upload the Astra addon zip under the 'Install a module' section in Magento Admin area.

Sign-up here to create an Astra account

Wait for a few minutes (max an hour) so that we verify your purchase from Magento's marketplace

Once your account is verified, simply click on 'Connect to Astra Button' here & login to your Astra dashboard. Astra will now be installed on your store :)