A standardised Sundanese script was recently included in Unicode, and now you can indeed type contemporary Sundanese script. Historically, there are other forms and standards and styles and whole other scripts for the Sundanese, but I know even less about those than the one that is notionally current. Read the history at Kairaga.com. Now read the Sundanese wikipedia article.
If I’ve understood the wikipedia page correctly (and I translated it from Sundanese, which I do not speak, so that’s not guaranteed) it’s like Thai and some other Brahmi-derived scripts in that there are primary consonants that a decorated with modifies to change the succeeding vowel. This is an abugida system. So the following should say “Lotekno”; Because there are modifiers attached to the consonants La-Ta-Ka-Na.
- Automatic transcription (missing the letter F, maybe others?)
To actually see the script (at least Aksara Sunda Baku, the new, consensus, modernized one) on your screen, you’ll need the right font installed, which took me a couple of tries.