First, let the salt dry, and scrape or rub off as much of the salt crystals (if any) that you can.
Second, wet the salt thoroughly, preferably with warm water, and vacuum with wet vac/ "Green Machine" type appliance. The salt will come dissolve and be vacuumed up with the water.
I've done this many times on car carpets (we have a lot of salt slush on the roads here in winter), and the Green Machine gets major salt encrustation off in the spring.