Presentations Aspect Ratio

[BillyRun]

The aspect ratio when working on a presentation is 16:9, but in the slide show it cuts off parts of the slide to make it 4:3. How do I change this, and also how do I change the aspect ratio cause I couldn't find anywhere to do that?
I'm using FreeOffice and the classic menu.
Thanks!

[SuperTech]

You can set the aspect ratio of your slides by menu command File > Page Setup> Slide Format tab > On-screen slide show dropdown.

Thanks