You may know about FTP, which is a common method for transferring files between servers. It's pretty powerful, and there are a lot of good FTP clients out there, but it's inherently insecure--- you must send your password unencrypted over the Internet.
For this reason, FTP is disabled on tentacle.net. You must instead use either SCP or SFTP to transfer files. Unfortunately, these methods are still less common than FTP, so there aren't as many programs out there that support them.
If you have chosen a graphical client (such as WinSCP for Windows or Fugu for Mac OS X), the connection procedure should be fairly self-explanatory. The host name you should use is tentacle.net.
If you are using a command-line client, you can use SCP or SFTP. People have strong preferences for either; you should probably try both out and see which one you prefer.
The basic way to send files using SCP and the command line is:
chaos % scp localfilename username@host:remotefilename
If you're transferring files for a web site (see Chapter 6, Web Sites), you should put them in your public_html directory. An scp example for the index page:
mycomputer% scp index.html firstname.lastname@example.org:public_html/index.html
Don't worry if you don't understand this--- once you gain a familiarity with the UNIX command line, it'll start to make more sense.
Most graphical web-page editors (like FrontPage or Dreamweaver) only support FTP or WebDAV from inside the program itself; you'll have to transfer the pages manually.