Hi, it seems that you are using DFGET and don't know how to operate it.
Please insure you have downloaded the latest FULL package which includes the Apache Commons.
Here's the download button:
Extract the zip and open the terminal or command prompt at the folder and launch the applicant by doing:
java -jar dfget.jar -help
This will show DFGET's help menu and shows you the syntax of DFGET.
Here's a example of downloading example.org and putting it inside of our home directory in a file called index.html.
java -jar dfget.jar http://www.example.org ~HOME/index.html