How do you use longingly in a sentence?

Synonyms: appetency, appetite, craving, drive, hankering,hunger, itch, jones [slang], letch, desire, lust, passion,pining, thirst, thirstiness, urge, yearning, yen

Examples of LONGING

1. They looked with longing toward freedom.
2. She cast a look of longing at the shop window.
3. She never told anyone about her secret longings.

Definition of LONGING: a strong desire especially for something unattainable :craving

You can use it in many ways but if you want to use specifically "longingly", you may say:

She glanced longingly at his back, knowing that they may never see each other again.

He stared at the cake longingly as the waiter carried it past his nose, to another nearby table.

I longingly looked at the beautifully wrapped gifts underneath the tree, staring especially at at the silver one with a pink bow, a gift to me from my sexy boyfriend.