How can you use a sentence grinning?

You can't actually use a sentence "grinning". "Grinning" is a verb, describing an action, not a thing you can use.

You can, however, use a sentence *to describe* someone grinning:

* "She grinned at him, her eyes sparkling."

This sentence uses the word "grinning" to describe the action of the person in the sentence.

Let me know if you have any other questions!