Touch the tip or front edge of your tongue to the roof of your mouth just behind your teeth. Keep your jaw relaxed. Stop the air, then release with a puff.

Americans pronounce tissue as TIH-shoo (/ˈtɪʃu/). Stress falls on the first syllable — keep everything else short and quick. You'll hear it in sentences like "She works in a pathology lab analyzing tissue samples".
Record yourself saying "tissue" 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 TIH — keep everything else short and quick.