You can access your FTP from a browser or an FTP program.  Here's how:

To access your FTP from a browser you can go to ftp://ftp.websiteforge.com/

And then login with your username.  (which looks like this: YourUsername.websiteforge.com) (YourUsername refers to the user name that you login to your members area with.  So if you go to www.websiteforge.com and login with JohnSmith as your username then your login would be JohnSmith.websiteforge.com)

Your password, is the password that you login to your members area with.

If you are using a FTP program, then your Server address would be:
ftp.websiteforge.com

and you will use the same instructions above for the Username and Password.

You can also access FTP from within your members area.

When you go to "manage images and files" there is a link on the bottom left hand side that reads "upload via FTP"

see screenshot: