We have form 1095-c. In this form, the employee required contribution is about $1000. Where can we enter this amount?

Nowhere. A 1095-C form is not inputted, and the data on it is also not inputted.

Your employee insurance costs are already pretax. Your benefit is built into Box 1 of your W2. You cannot deduct your costs again.

The 1095-C form verifies your coverage eligibility. If you had insurance through your employer, your tax benefit should already be encompassed with your Box 1 wages.