Drop your jaw slightly with relaxed lips. Touch the tongue tip behind the bottom front teeth and arch the top-front toward the roof.

Americans pronounce immunity as ih-MYOO-nuh-tee (/ɪˈmjunəɾi/). In "immunity", the "t" between vowels sounds like a quick "d" — the tongue briefly taps the ridge behind the upper teeth. This is called the Flap T, a small move that separates 'classroom' from 'native'. It comes out as ih·MYOO·nuh·tee. Stress falls on the second syllable — keep everything else short and quick. You'll hear it in sentences like "She was granted immunity in exchange for her testimony".
Record yourself saying "immunity" and play it back. The mic stays on your device — nothing's uploaded.
4 syllables, 7 sounds. Tap a syllable to jump to its row, then explore each sound's mouth shape and how it's made.
The textbook way isn't wrong — it's just not how anyone actually says it.
In "immunity", the "t" between vowels sounds like a quick "d" — the tongue briefly taps the ridge behind the upper teeth. /t/ or /d/ becomes a quick tap [ɾ] — sounds like a soft D. The tongue briefly taps the ridge behind the upper teeth.
Stress falls on the second syllable, not the others. Stretch MYOO — keep everything else short and quick.
Don't pronounce the second syllable too fully. The unstressed syllable reduces to a schwa — the lazy "uh" sound — in casual speech.