Honestly, not much to be said here. Coolant leaks are a bummer. You gotta find out where it is leaking, and replace the part. Sometimes a hose bursts or comes off, sometimes it is as simple as tightening down a hose clamp. But get in there and find out whats going on. If you are lucky and the hose has split, you may be able to cut away the bad part and have a little extra to pull onto your pipe, and ride away right then.
Remember straight water will substitute for coolant in a pinch, but replace it back with 50:50 coolant/water mix as soon as you can.