Welcome to the world of "accrual". Most people think "well if I send someone money, that's that. It's their money now". The IRS (and large corporations) think "If you send money it's still your money until some form or invoice happens to make it theirs".
So if you sent $1000 to the gas company that's your $1000 credit balance, and you can ask for it back. After a month and you have a $100 gas bill, they deduct the $100 and now you have $900 on credit and you can ask for it back. Etc.
So when you send money to the IRS, that goes into YOUR account at the IRS for that tax year. It's still your money up until you do a separate thing called "filing your taxes". Or alternately you can do nothing for 3 years and the money just becomes theirs.
So if you have not "filed your taxes", do so. The end of the form will show you owing a refund, and the IRS will send your refund.
If you already filed your taxes, this should have happened automagically. However if it didn't because you filed your taxes incorrectly, you can re-do your taxes and then file an amended 1040X, and IRS will issue a refund once they process that. However being a specialty thing, this is a lot slower and can take up to 6 months.
Some people simply let the IRS take their withholding, and knowing they're owed a small refund don't bother to file their taxes at all (and let the IRS keep it). Nothing wrong with that if that's your cup of tea... but if you now change your mind, guess what? There is no penalty for filing taxes late if the IRS owes you money. Not only that, once you have your "tax filing chops" down, you can go back 3 years and collect refund on 2020 or 2021 taxes (to get 2019 you'd have to file with a postmark of today April 17 2023).