You misunderstand.
To benefit from the full credit, your tax liability must be more than the credit. Your tax liability (not counting self employment tax) is what you owe to government after all other taxes, credits and deductions. It's shown on line 24 22 of your tax return. For example, if you have $10,000 of withholding and you get a $1000 refund, your liability was $9000. Likewise, if you had $10,000 of withholding and you owed an extra $1000, your liability was $11,000. It's what the government gets to keep at the end of the filing process.
If your tax liability will be less than $7500, you would need to find some way of increasing your taxable income, like maybe changing from pre-tax to Roth retirement contributions. But if your liability is already more than the credit, you don't need to do anything to get the credit refunded to you. You certainly can change your W-4 to have less withheld, so you would get a bigger paycheck and a smaller refund at the end of the year. But changing your W-4 doesn't change your tax liability, it only changes how and when you pay your taxes.
