Before you proceed, you need Spaces installed on your phone.
How to set a member as Owner?
Step 1 - Open the Space for which you want to set member as Owner and navigate to the Members Tab. Then. click on the member that you want to set as Owner
Step 2 - From the options below, select on Set as Owner.
Step 3 - It would open a confirmation screen, here click to confirm for Set as Owner.
You are done!