With a Mac:

1. In Character Viewer, under “Symbols” you’ll find Phonetic Symbols. Select the character you want, and click the “insert” button (or double-click the character). You may need to enable the character viewer – here‘s how.

2. You can also install this IPA keyboard layout.

With Windows:

1. You can install this IPA keyboard layout.

Any OS:

You can copy and paste from this unicode IPA chart, or this one.

Diacritics

Both the mac Character Viewer and the web-based IPA chart (and maybe others) include diacritics that can be combined with other characters (e.g. the voicelessness diacritic [b?]). These may align incorrectly in the WordPress “Visual” editor, but they will display correctly when you publish.