The child must have been under age 17 at the end of 2016.
The amount of child tax credit you can receive is limited by your tax liability.
If your tax liability is zero, then you are not eligible for any child tax credit.
However, if you qualify for the Child Tax Credit but do not receive the full amount, and if your earned income is greater than $3,000, you might be eligible for the Additional Child Tax credit. The amount will vary from $1 if your earned income was $3,004, up to $1,000 if your earned income was $9,666 or more.
Too high of an income will reduce or eliminate the CTC also. For a single taxpayer (or HOH) the phase out starts with a AGI of $75,000 (MFJ $110,000, MFS $55,000).
The actual amounts on your tax return will depend you your filing status and the number of child dependents.
You can look on line 35 on the 1040A for for the Child Tax Credit (line 52 on the 1040).
See IRS Pub 17 for full information: