How can I tell if I can add a front brake to my cruiser?
To install a front brake you will need to have a fork that will accept the brake caliper.  There are three potential options for this: A standard road caliper (hole through the fork crown), cantilever/ v-brakes ( one post on either side of the fork blade) or a disc mount (bracket at the end of the fork on the non-drive side).
The Masi Soulville should have the first option, a hole drilled through the fork crown for installing a standard road caliper.
You will need to get a road caliper that is intended for use with a flat bar brake lever, as many road calipers are intended for use with drop handlebar levers.