How do I pay in quarterly taxes when taxes aren't held out of a paycheck, and part of the paycheck is considered "non taxable housing allowance" from a church?

In March of this year, my husband took a full time position at a new church. We currently live in Texas, and this church is in Louisiana. He has no taxes held out of his check, and part of the check is a housing allowance that isn't taxed at all. We've never been in a situation where taxes were not held out of our paychecks and this is all new territory that I know nothing about. How do I pay in our quarterly taxes, or begin to even know WHAT those taxes should be, and does living out of state make a difference? I don't want to get into trouble come refund time.