There are several ways of accomplishing this. Open up Eclipse Preferences, type in Templates as your Filter, then select Java->Code Style->Code Templates. In the Code Templates widget, expand the Comments widget:
Looking through the expanded selection, you can see that there are templates defined for Types and Methods, amongst others. Select whichever template you want to edit, then click ‘Edit’. You can now change the template as you see fit, for example by adding @author ${user} or whatever else to it:
Click ‘Ok’ out of all the dialogs to complete and save.