Yes it is safe. I have it running on 3 devices. To install a new source, open Cydia and at the bottom, select sources (2nd from left). Select edit on top right and then add on top left. Add whichever source you want and select Add Source. After that you'll see some info scrolling on the screen, when it's done select return to Cydia.
Thank you so much menard_00 it's working now.
