https://cdn3.iconfinder.com/data/icons/ultimate-social/150/17_google_play-512.png     If you are having this error message "Android App Not Install. An existing package by the same name with a conflicting signature is already installed"
while trying to install an app.

here's is a solution to it.
downloading a file from some other websites can cause such problem.
try installing the app from plystore.
it's free and safe.
I've  tried it on several apps and it worked for me.  ;)