How do I input symbols from the International Phonetic Alphabet? I have looked at the Editing Help but there is nothing about it.
Some IPA symbols have HTML entity codes with more or less logical names/abbrevations, so you can type them in plain ASCII:
But most of them, like the schwa, only have numbers, which will be hard to remember:
A full list is available here.
For an occasional user, the keyboard linked to by M.A.R. would be my suggestion:
If you want to type a lot of IPA, it might be more convenient to install the Keyman IPA layout on your computer:
This is free and cross-platform, and you can even try it out right in your browser! But make sure you read the docs first, since you probably won't be able to figure out how to use it just by guessing.
(If you search online you might find recommendations for KMFL or Ekaya – essentially free alternatives to Keyman – but thanks to SIL International, the Keyman software is now free on all platforms, so you don't need to download KMFL or Ekaya anymore.)