Distributing files to you from sputnik - for that purpose, there is a user account on sputnik named "public". Its password is as given in class (email me a request if you don't remember). It contains a lot of files. You can download them using sftp/scp with those account credentials. (You may be familiar with anonymous ftp. This is comparable to it, however ssh/sftp/scp have no "anonymous" feature so this is a functionally similar workaround. Unlike your own home directory, you can only download from public's home directory, not upload.) I will from time to time ask you to acquire files from this source.
To get a file I've placed in the home directory of user account "public" you might use scp/sftp from the linux command line, or Filezilla (on linux, Windows, or Mac) which is just a front end to the same thing as scp/sftp. If you use Filezilla, prefix the name of the target "Host" with "sftp://" or put a "22" in the "Port" field. This causes Filezilla to use sftp (the secure ftp that is part of ssh) rather than the regular, older, unsecure/unencrypted ftp protocol which it would use by default.
If you used scp to get a file named "softwaresecurity.zip" for example, it would be done like this:
scp firstname.lastname@example.org:/home/public/softwaresecurity.zip . (don't omit the dot)
You would be prompted for the password of user account public, and would supply it. The file would transfer and you would find it sitting in your current directory (the dot is shorthand for "my current directory").