First, make sure you're looking at the working copy. Look for the drop-down to the left of the title. If it says Current, click it and select Working Copy.
If you're the lock owner:
You should now see options to either Commit Changes you've made, or Break Lock and discard those changes. You also continue to edit and save changes to the Working Copy.
If someone else is the lock owner:
The lock owner will be listed in the message bar at the top. You can reach out to the lock owner and collaborate on changes or have them reassign the lock to you. If you have the correct permissions, you can also either Break Lock (changes will be lost!) or reassign the lock to yourself.