1. First you have to navigate to the user account to whom you want to change the Owner.
2. In the below screenshot you can see the contact details we will change this contact owner.
3. Then hover over the owner name, and it will show you the pencil icon click on that it will show you the dropdown having the Owner. From that, you can select the desired one.
4. When you select the desired one, then your owner will be changed.
