There are several ways you can rename your section and subsection titles in a PowerPoint presentation.
Change the name on the divider
On your section or subsection divider, select the title placeholder and update the title. Use the Refresh button in the References section of the UpSlide ribbon. Once the refresh is complete, the new title is displayed in your table of contents.
If you don't have a divider slide for your section or subsection, go to the References section of the UpSlide ribbon and click Options to enable them.
Change the name in the Outline
Go to the References section of the UpSlide ribbon and click Outline to see the structure of your presentation. Right-click the section or subsection you'd like to update and click Rename.
Use the Refresh button to make the change visible in your presentation.