Most english speakers here will have an english-language keyboard and will often be confonted with the problem of how to type special characters for foreign languages.
In german the problem will be the umlaut vowels - "the ones with the dots over them" - and the ß or scharfes-S
Here is a (fairly) simple way of doing it in Windows.
You need the numeric block on the right of the keyboard ("num lock" on)
Hold the Alt key down and type in the following numbers
(or simply use the alternative spelling, without umlaut)
ä = Alt 0228 or ae
Ä = Alt 0196 or Ae
ö = Alt 0246 or oe
Ö = Alt 0214 or Oe
ü = Alt 0252 or ue
Ü = Alt 0220 or Ue
ß = Alt 0223 or ss