Thread: Upgrading from 3.1.8 to 3.1.9

Upgrading from 3.1.8 to 3.1.9

I need to upgrade from 3.1.8 to 3.1.9. Classipress is already public and there are ads posted. When I upload 3.1.9 zip file through the Install Theme Admin I am getting that the folder already exists and stops the installation. What can I do? I want to keep the ads that have been posted and I don't want install from scratch.
Help appreciated.
(Note: I found a thread with a similar problem but in his case the site was not public and did not have ads)
Need an answer urgently.