If what you received in the mail was a paper showing how much you received for being a foster parent, you do not need to enter that information. You do not need to report Foster Child payments as income. This is not regarded as income.
Please see this from the IRS:
It was a paper stating keep with your taxes, it had the days I had her and the amount you can claim, i didn't receive any money for her being in my house
If the child was with you for more than half of the year, you would be eligible to claim them for Child Tax Credit as long as no one else would be claiming them.
The Child Tax Credit is worth up to $2,000 for each child who meets the following requirements:
Or, you may be able to deduct your unreimbursed foster care expenses as a charitable donation. The expenses are deductible if the agency or organization that placed the child with you can receive charitable donations (so your local social services department would not qualify).