If you're employed full time at a company, one of the first things you did when you were hired was fill out IRS W-4 tax form. The information you provide on the W-4 determines how much money is withheld from your paycheck each pay period and paid toward your personal income taxes. The calculation is based on the number of exemptions you claim. The more exemptions you claim, the less money is withheld for tax purposes. (Remember that your personal exemption was removed with the 2017 tax law reforms, so the exemptions you're taking will be for other family members.)
If your goal is to increase the dollar amount you receive in your tax refund, you can go to the human resources department and request to change your W-4 tax form. When you reduce the number of exemptions on that form, then a larger amount of money will be withheld from your check each payday. Your tax refund will therefore be larger. The times of year you're allowed make this change are dependent on your company's policies, but generally, it may be made any time of year.
If you need help figuring out how many exemptions you should claim based on the size of your family and your income (including jobs held by a spouse), use the IRS withholding calculator. Keep in mind that the calculator is designed to help taxpayers "break even" by withholding the exact right amount of tax from each payment so they don't owe money in April or receive a big refund check. If you want a bigger refund check, simply subject a few of your qualified exemptions and more tax will be withheld during the year.