Hi Johnsonjoy,
1. Are you facing issues with booting in to desktop?
2. Which program are you trying to install?
3. Do you know that location of the programs .exe file?
It depends what you mean. Installing software directly from the internet or installing software you have already downloaded.
You cannot install software directly from the internet with a command prompt. You could start up a pre-downloaded installer in CMD though by telling it the path of the file, which is somewhat pointless since you could have gone to the location without command prompt.
Reply with more information to help you better.