Under normal circumstances, the man should first have his glans fully exposed and his penis in a fully erect state before wearing a condom. However, if the glans is not fully exposed, putting on a condom may affect the erectile function of the penis or affect the overall sexual experience during sex. If the glans is not exposed when the penis is in an erect state before wearing a condom, it is usually due to circumcision. In this case, it is best to turn the foreskin over to reveal the glans by artificial means, but if this method does not work, you need to consider going to the hospital for circumcision.