Define "correct". Is it counting too many / too few miles? Or have you somehow wound it on / back during work on your car? Whichever it is, you are best getting it done at a reputable dealer, so that you have a legitimate record of the work for the car's log-book, preventing yourself getting in legal bother later, and maintaining the car's resale value at a later date.
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In the USA, it's illegal to alter the odometer. If your odometer is reading incorrectly, then so is your speedometer. Two likely causes of incorrect speedometer/odometer readings are 1) replacing the differential with another having a different gear ratio 2) changing the size of the tires. Remedy either of those to solve the problem.
Has it gone wrong because you have fitted tyres with the wrong rolling radius to it ? See a dealer.
Odometers, including the digital variety, are deliberately resistant to tampering in order to prevent folks from "rolling back" the odo in an attempt to sell a car for more than it's worth. So the simple answer is "you can't." I'm not even sure a dealer can do so without completely replacing the computer module -- which costs about a kilobuck, last time I checked. If there's a Good Reason why it's wrong, I think your best bet is to get someone (your regular mechanic?) to sign a document stating that they saw it before and after the error occurred and can attest, as an expert, that there's no way you could have put that many miles onto it between those two times.
Take it to a spedometer shop and they can reset the computer. Take it to the dealer and they can reset the computer. Locate or buy a service manual and the software and you might be able to reset the computer. I don't think it's resetable any other way. It's not "user" easily. I've bought service manuals for other cars before and they run about $90. Then again someone else might have a better answer for you.