How to best handle stock grants and losses?

Hi! Thank you for your advice!

 

I am an employee at my first public tech company, and was granted stock as part of my comp. It vests over 4 years, and I am coming up on my 2nd year, when the newly vested shares will automatically get transferred to me. It’s lost value since it was initially granted. Even though I’m not cashing out on the stock and plan to just hold it in Fidelity, is there a way I should be filing my taxes so that I can maximize my losses, or does that only occur when I actually sell the shares for cash? Thank you for your advice!