I assume you’re writing in American English, but you might still encounter accented characters in foreign words. Foreign words arise in two situations:
In proper names, like people and places (Albrecht Dürer, François Truffaut, Plácido Domingo). In names, accented characters must always appear accurately. Otherwise, the name is misspelled.
In loanwords used in American English. Some of these words have become naturalized citizens and should be spelled without accents—naive for naïve, melee for mêlée, coupe for coupé. Others have not and should not—cause célèbre, piña colada, Götterdämmerung. Check a dictionary or usage guide.
How do you type these? Consult the chart of common accented characters.
Proper names are not italicized, but loanwords sometimes are, depending on their degree of assimilation. Again, check a dictionary or usage guide.
The German letter
Eszett(at left), formerly a special ligature, in 2017 became a full member of the Standard German alphabet. Originally, it took the place of ssin a word like Straße. But in today’s Standard German, words like Masseand Maßeare distinct. Switzerland, however, has always ignored the Eszett, and just uses ss. And no one uses the Eszett with all caps. Except those who do. Your best bet—follow Switzerland’s lead and ignore it. Even if you place the Eszett correctly, it’s less common to readers of American English than the usual accented characters, and it can easily be mistaken for a letter B or a Greek beta ( β).