Depending on user role permissions, you can reassign ownership of a person to another user on your account from either the person's profile page or the Owner column in a People list view.

From a Person profile page

From the person profile page, click the user's name next to owner and choose a user from the dropdown menu. The new owner will receive an email notification that a new person has been assigned to them.

While you are in the person record, you can also press Edit Person on the top right portion of the screen and select the new owner next to the Owner field.

From a People list view

Reassign individual people in a list view by clicking on the owner cell in the then selecting a new owner from the drop-down menu.

Reassign people in bulk by selecting them using the checkboxes on the left-hand side and clicking on the Reassign button. You'll be able to select the new owner from a menu after doing so.