because your site was designed in NOF.
You'll upload to your WebMania space in just the same way - direct from NOF. If you have a domain name in mind I suggest that you register it with WebMania and get yourself started in your new web space as soon as possible. Come back to this thread when you need help.
Your computer will cope just as well - all the files will be held on the server, although NOF will create a backup on your hard drive as it does now. Just change the publication details in NOF when you get them from WebMania - we'll help you with that.