As soon as you add a subdomain, add-on domain or parked domain to your hosting, an SSL will be installed for it automatically, though it can require up to an hour to complete installation and appear as active.
If more than one hour has passed, you can check the following:
The domain is not pointing
SSL installation can proceed if your domain is pointing to Hostinger. If the domain is not pointing to Hostinger yet, above on the same page you will see a message like this:
Just click on Learn more or check this article for guidance on how to point your domain. The issue should be resolved in less than 24 hours after the domain is pointed correctly.
If you have verified that your domain is pointing and propagated, and it still appears as failed, you can try reinstalling by clicking on the options button (⋮) → Reinstall:
If you followed all the steps and the Reinstall button didn't help, contact our Customer Success team