The method by which files are transferred to the web server is called "FTP" (File Transfer Protocol). FTP is designed to provide you with access 24 hours a day. As such, you can create and maintain your web pages on your own computer and upload files to your Website at your leisure.
There are many "Free" ftp clients. Searching google is a good first step. "Filezilla", http://filezilla-project.org/, is a good free FTP client.
