If you sold the stock and then just gave the cash to the church, then you just enter this as you would any other cash contribution.
If you gave the church the stock and they sold it, then you show this on form 8283. Attached are the instructions for this form:
https://www.irs.gov/pub/irs-pdf/i8283.pdf
Regardless of which method you used, you need to make sure you get a receipt and the language that no goods and services were provided (assuming that is true). This is critical or you will lose your deduction if you were to be audited.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
