We don't offer DNS hosting. Most large domain registrars supply this for free, but if yours doesn't there are several free options out there. One free provider that some of our users use is Namecheap.
If you would like to use Namecheap's free DNS hosting you will first need to register an account at http://namecheap.com and then go to https://www.namecheap.com/domains/freedns.aspx to setup the DNS for your domain.
Next you will need to go to your domain registrar and point at Namecheap's nameservers. Namecheap have some information about how to do that here:
Once your domain is pointing at Namecheap's nameservers you will be able to configure your DNS settings to point to Dropr.