To renew a domain you will need to log in to your SW Panel account. Once inside, go to the tab Domains and SSL -> Domain portfolio that you will find on the left side menu in blue:
Locate the domain name you want to renew, drop down the options menu on the right and click on "Renew domain name ".
It doesn't matter when you renew your domain, it doesn't matter how much time is left to expire, you will never lose days of validity. You will always add one more year to the current expiration date of the domain.
You will see the text "in the renewal cart " and right at the top it will have been added to your cart. Click on the same cart icon to finish the process:
Indicate the number of years you want to renew it and click on "accept domain cart ".
Domains can only be renewed for a maximum of 10 years.
In a few minutes, you will be able to see the new expiration date of your domain.