The image of water is reflected in many instances in the Bible - the Baptism in the Jordan; the ritual of washing of the feet at the Last Supper, to name but a few.
Holy water dates back to the earliest days of the Christian Era. The “Apostolic Constitutions”, the redaction of which goes back to about the year 400, attribute to the Apostle St. Matthew, the precept of using holy water.
Gregory of Tours (De gloria confess., c. 82) tells of a recluse named Eusitius who lived in the sixth century and possessed the power of curing quartan fever by giving its victims to drink of water that he had blessed. We also see the miracle of the spring of healing water, gifted by Our Lady at Lourdes.
Using water that has been blessed by either a priest or a deacon, we can use this sacramental in a number of different ways...
Your home is regarded as your domestic church - place a bowl of holy water at the front of you door, blessing yourself when entering or leaving your home; while praying for protection for all who dwell there. This is similar to entering and leaving the church. Likewise you can also bless each room of your home or invite a priest to do this for you.
Bless your car! Yip! thats right, use holy water on and in your car. We use our cars daily for commuting here and there, it's comforting to know that a you can recieve a blessing on your car, invoking protection on your journeys and passangers. Again you can ask your priest to do this for you.
St. Francis had an affiliation with all of creation, particurlary animals - the blessing of pets is common for many animal lovers, you can do it anytime! Just sprinkle your pet or livstock with holy water and pray for God’s blessing upon it, thanking God for the whole of creation.