If you purchased a domain at Hostinger, you can easily renew it on the Billing → Services page. If the domain name is available for renewal at the moment, you will see a Renew now button:
It will direct you to the payment options such as billing period and payment method, from where you will be able to renew your domain by clicking Complete payment:
To see the renewal price of your domain at any time, go to Billing → Services - you will find a column with the Renewal price of all your purchased services:
NOTES:
Domain renewal is possible only 2 months before the expiration date or less (based on the TLD)
You can renew your domain and other services automatically, you only need to enable the Auto-Renewal option
If your domain is registered elsewhere, you can transfer your domain to Hostinger to renew it here. Alternatively, you would need to renew it at the current domain registrar
If you encounter any issues during the domain renewal process, contact the Customer Success team