Thus used non-superstitiously, modest amounts of salt may be sprinkled in one’s bedroom, or across thresholds to prevent burglary, in cars for safety, etc. A few grains in drinking water or used in cooking or as food seasoning often bring astonishing spiritual and physical benefits, as I have personally witnessed many times. As with the use of Sacraments, much depends on the faith and devotion of the person using salt or any sacramental. This faith must be Jesus-centered, as was the faith of the blind man in John 9; he had faith in Jesus, not in the mud and spittle used by Jesus to heal him.
Any amount of salt may be presented to a priest for his blessing, using the following official prayer from the Roman Ritual:
“Almighty God, we ask you to bless this salt, as once you blessed the salt scattered over the water by the prophet Elisha. Wherever this salt (and water) is sprinkled, drive away the power of evil, and protect us always by the presence of your Holy Spirit. Grant this through Christ our Lord. Amen.”
As to where to keep it, just make sure it is in a specially marked container so that it isn’t confused with your table salt. I have been given blessed salt in film cans, baggies, zip-lock bags and canisters. With holy water, I get it from the church in an empty bottled water bottle then label it so I don’t confuse it with ordinary bottled water.
And from Catholic Encyclopedia