In order to request our free migration service, everything you should do is write us at our support email or contact us through the contacts form and provide us with an access to your current help center.
When we hear from you, we will evaluate it and come up with an estimate how long it will take us to complete the migration for your case. On top of migrating all your content, we can also completely migrate the styles of your previous help center if you'd like us to do so. Just let us know.