GoCentral is on a platform of its own and the site is not transferable. You would need to purchase a new hosting account (cPanel or WordPress for example) and then migrate the content manually to the new platform.
Don't unpublish the current site until you have everything setup on the new hosting. Once everything is setup the way you want, then move your domain over to the new hosting and cancel GoCentral a week later. This way you can avoid any potential down time.
Judith "Do one thing every day that scares you." ~ Eleanor Roosevelt