The statement after you check the appropriate boxes explain that if you DO have the social security and medicare tax withheld on you W2, then go back to uncheck Religious Employment.
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"Not everyone who works for a church or religious organization is religiously employed. If this W-2 has Social Security tax withheld in Box 4 and Medicare taxes withheld in Box 6, select Back and uncheck the religious employment box."
Press Continue to enter your housing allowance. Click the image attached to enlarge and view for assistance.