The regular child tax credit ($1000 per child) can only be used to reduce income tax. It cannot be used as a credit against self employment tax. Since your income is not high enough to have any income tax liability (line 47 of form 1040 is zero), you do not get any Child Tax Credit (line 52 of form 1040).
But,
if you have more than $3000 of earned income, some or all of it is usually
given back to you thru the "Additional Child tax credit". That is,
part of the CTC may be on line 67 of form 1040 instead of line 52 . The
ACTC is calculated on form 8812; that form is not viewable in the online
version of TT until you have paid for your return. But, the ACTC is basically
15% of your earned income over $3000.
