Raise the back of your tongue to touch the soft palate (velum). Stop the air, then release.

Americans pronounce cow as KOW (/kaʊ/). You'll hear it in sentences like "How goes the cow?".
Record yourself saying "cow" and play it back. The mic stays on your device — nothing's uploaded.
1 syllable, 2 sounds. Explore each sound's mouth shape and how it's made.