For example, in Database, at the All Database Items screen, press (MENU) File Modify Database. Press (F2) (Add) and enter a name in the Field Name field.
For this example, type Client. Place an & symbol in front of the letter you want to assign as a shortcut key (e.g. in front of the e in Client), tab to the Field Type field and select the option you want, then press (F10) (OK). In the future when you want to go to the Client field, press (ALT)-(E).