While HostGator cannot modify nameservers at third party registrars on your behalf, we can provide you with instructions on how to do so. Here's how you can change your nameservers at Tucows.
Tucows primarily offers services to resellers, but does have a retail brand called Hover. If a WHOIS search indicates that Tucows is the registrar, the domain itself is most likely registered through one of their many resellers or with Hover.
Step 1: Find Out Nameservers for Your Hosting Account
The first step is to find out which nameservers you should use for your HostGator hosting account. This varies by server and type of hosting. For instructions on how to find out your nameservers, please read the article:
Step 2: Changing Nameservers
You will need to visit the website or contact the reseller that you registered your domain with to change the nameservers. Since Tucows offers resellers an API, reseller websites can vary dramatically; so it is hard to give specific instructions that would work across all Tucows resellers.
Tucows does have a retail brand called Hover, and if you registered your domain through Hover, then you can find the directions here: