I installed the "Contacts" app in the AppCenter and it does not appear in the Applications list (slingshot). How do I run it?
Open terminal and paste
sudo nano /usr/share/applications/org.gnome.Contacts.desktop
Look for
OnlyShowIn=GNOME;Unity
and add Pantheon after Unity
OnlyShowIn=GNOME;Unity;Pantheon;
Then click ctrl+x and then y and Enter to save it.
Now search for contacts in Slingshot.
There are two contacts apps currently in AppCenter, but if you mean the one with the brown icon, just run:
gnome-contacts
(Full path is /usr/bin/gnome-contacts
.) The easiest way to add a Applications menu (called Slingshot) item is likely MenuLibre.