How can I get a corn tortilla to be pliable enough to work with?
You need to warm them up a bit. There are a number of ways to do this


20 or 30 seconds on a griddle (or a comal if you have one)
wrap a stack in foil and place in 325 oven for until warm
wrap a stack in a clean towel and steam them using a steamer
slightly moisten a towel and wrap it around a stack and microwave them for a bit


If you've warmed them and they are still tearing then your tortillas are no longer fresh.