After you file

...and you put your W-2 income into that "Form 1040" tax return .

The BUT point was that if you have self-employment income also, it won' offset the SE taxes for that....which is why they pointed to line 44 of the form 1040 that you sent/send to the IRS. because that line is what the credit would offset (or line 30 of last year's 1040A if that's what you actually filed for 2017).  Of course, this assumes your income for 2018 is similar to 2017.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*