how do I make a program executable through the command prompt?
 

I have downloaded, unzipped, and untarred a program called Opera. I want to be able to type the command opera in the command prompt, but I don't know what to do? If anyone could help me out I'd appreciate it a lot. Thanks.

If its installed and in your current $PATH, then just type: opera &

And that should be the command to launch it.

If its not in your path, cd into the directory where it is located and do a: ./opera &