Hi ! ...
Not knowing is nothing to be shamed about, none of us were born knowing. On this forum there is no such thing as a "dumb" question ! We exist here to guide and assist.
Bear in mind this is an open forum for the benefit of all. Thus all correspondence in respect to problem resolution is best conducted in the view of all, viewed by many and peer reviewed of all responses.
To address your present issue; Post back - copy and paste between code (#) tags at top of your post - the output of terminal commands:
relates the state of your installation at large.
sudo apt-get update
sudo apt-get upgrade
Package Management -> Applications and software::
Other Software tab: Standard install manages all installed applications with the database file /etc/apt/sources.list as the base (ubuntu Software Center is one front end for this utility) and when a Personal Package Archive for developed applications not in the standard files repository are made available to the public, that access is placed in the /etc/apt/sources.list.d directory (Other Software tab).
If you have a problem related to your sources list post back to us the out put of terminal commands:
We will determine where the fault lies.
ls -la /etc/apt/sources.list.d
just try'n to help