To adjust your withholding, you will need to complete a Form W-4 and give it to your employer. Be sure to ask your employer the number of allowances you are currently making. Then, compare that number to the number of allowances you get when you complete the new Form W-4.
-follow this link to print a copy of W-4-
You refund might have been bigger than expected for 2020 because of the Recovery Rebate Credit, the $10,200 unemployment comp deduction, or some other unique event. But that's no guaranty that these will continue for 2021, so keep an eye on your withholding as the year goes by.