Welcome to Apple's Discussions.
Two assumptions I'll make -
(1) That you are using Mac OS 9 (since that's the forum in which you posted)
(2) That you are after the umlaut characters and the funny double-S
If you currently have the US English Keyboard Layout active, you can do the umlaut by pressing the key-combo Option-u followed by the character you want. Works with capitals, tooExamples -
Option-u plus a types ä
Option-u plus e types ë
Option-u plus i types ï
Option-u plus o types ö
Option-u plus u types ü
Option-u plus y types ÿ
Option-u plus A types Ä
(etc.)
For the ß character, press Option-s. I think this may actually be a capital beta (Greek letter), but it bears a close resemblence to the old German character.
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You can also reset the keyboard to a German keyboard layout. This makes accessing some German and European characters easier, but means having to learn a new pattern for the keys. If you want to try that, make sure that German is checkmarked in the list in the Keyboard control panel. Once more than one language is checkmarked in that control panel, a small flag icon will be added to the main menubar, which represents the keyboard language menu. You can then use that new menu to select the language layout you want activre. You can use the utility Key Caps (usually found in the Apple menu) to see what's where in the new layout.