Hallo Victoria, guten Tag.
You can get the special characters using a pop up keyboard in the "write it" Test, but this doesn't work in the forum.
This link shows you the German keyboar layout:
If you are using Windows 10, you can switch to a German keyboard quite easily, see:
There is something similar in Windows 7 but it is not convenient to use.
I don't have an apple PC, but I found this link:
If you are using Windows, you can also use ALT codes:
German character alt codes
Press and hold the ALT key then type in the number below using the numeric keypad, then release the alt KEY.
lower upper case
ä 132 0196
ë 137 0203
ö 148 0214
ü 129 0220
You can google Windows ALT codes if you want to know more.