how can I force quit just my "finder" app on my Mac book?

You cannot quit Finder. The only way is to relaunch it. Access the Force Quit menu in OS X by pressing the command +option/alt+ escape keys together, click Finder in the menu that appears and then click Relaunch.

Open the Task Manager by pressing  Option+ Command+Esc, then click on "Finder" to force restart the Finder.

Second this. OP, Finder is responsible for much more than you think - it has to remain running in order for you to access your files and view your desktop.