When you see on a schedule that a specifc park has Extra Magic Hours (EMH) in the morning, it means that park opens (to Disney resort guests only) one hour earlier than the published opening time. When a park has evening EMH, it means it stays open 3 hours later than the published closing time. For example, during a busy season, like let's say Easter, if Magic Kingdom is normally open until midnight, it will be open until 3:00 a.m. on EMH nights for Disney resort guests.
About 2 hours before the normal closing time, you look for Disney cast members (CMs) handing out bracelets. Every person in your party needs to show their room key/resort ID in order to get a bracelet. Once EMH starts, only people with bracelets are let into rides/onto attractions. For morning EMH, there are no bracelets, but you need your resort ID to even get into the park before the normal opening time.