At Hostinger, you can restore a backup by logging into your cPanel account and navigating to Files → JetBackup 5 section:
Once there, click on the desired option:
Select the available backup and click on Restore:
After a few minutes, depending on the size of the selected backup, the restoration will be completed.
For cPanel reseller plans, you can also use this feature to restore backups for your cPanel customers. If JetBackup 5 is missing on your Reseller client plan, you can enable it by navigating to the WHM → Feature Manager → Edit Features section.