msttcorefonts download stuck?

Today tried to download 'msttcorefonts" via Ubuntu Terminal program seems to get stuck on the user agreement without downloading or installing, so I chose to cancel the hung-up download attempt.

Q: Tried to use SPM but got the following error "This usually means that another package management application (like apt-get or aptitude) is already running. Please close that application first.'

What do I need to do, to free up 'Synaptic Package Manager?'

Thank you in advance I just downloaded Ubuntu yesterday & absolutely love it.

-Bearz