Running a presentation a larger external monotor

I will be giving a presentation using a larger screen than my 17 inch monitor (presentation will be give on a Windows machine, but created under Kubuntu and LO Impress)

I do not know the diemsions of the external screen

How can I ensure that my presentation fills the screen?

Wili I have image quaility issues on expansion? the slides will be images (in most cases).

If so, how can I correct for the quality issues?

Thanks

LO ver 4.2.7.2.