To cash a third-party check, you and the check's payee must go to a bank that cashes third-party checks and show proper identification. The payee signs the check's back and writes "pay to the order of" and your name above the signature line. Then you sign the check.
Cashing a third-party check represents a larger risk to a bank, so you may have better luck trying to cash the check at the issuing bank. The bank may charge a check cashing fee for this service. Your personal bank may also cash the check or accept the check for deposit, especially if you have enough money in your account to cover the amount of the check if it is returned.