If you are on a Mac or iPad all you need to do is hold down the key, s in this case, and you will get options. Just select the right one.
So, the options for s are š, ß, and ś. This is your name: Schoißer. As a German name you can also write Schoisser.
There are some less common diacritics, so you need use an alt-code if your software allows it, or cut and paste: Ů and ů. The ring diacritic is called kroužek in Czech.
You can also use a font map, ie, “insert symbol” in a word processor.
If you are doing a lot of these you can install a language or international keyboard. Doing a google search for international keyboard and your operating system will get you the instructions, which are pretty simple as I recall.