Touch the tip or front edge of your tongue to the roof of your mouth behind your teeth. Air flows through your nose.

Americans pronounce nephew as NEH-fyoo (/ˈnɛfju/). Stress falls on the first syllable — keep everything else short and quick. You'll hear it in sentences like "She is the legal guardian of her younger nephew".
Record yourself saying "nephew" and play it back. The mic stays on your device — nothing's uploaded.
2 syllables, 4 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.
Stress falls on the first syllable, not the others. Stretch NEH — keep everything else short and quick.