By default an invoice will be generated 2 weeks prior to a domain name expiring at which time you can log into your billing control panel at http://cp.hostek.com and pay the invoice to renew the domain.

If you want to renew it prior to the 2 weeks you will need to log into your billing control panel at http://cp.hostek.com, click on My Domains, then click on the green arrow next to the domain you wish to renew and then click on Renew Domain.

This will create an invoice which you will need to go and pay to have the domain renewed.