How can I "autostart" an impress presentation?

LibreOffice version 4.2.3.3 in English - impress presentation.
Mac osx 10.7.5 in English. (I also use Ubuntu 12.04 in English.)
I want to switch from ppt to impress but am having a hang-up with impress not opening the presentation directly. I can’t find an option for saving as autostart. I have saved as .pps but it is usually very slow in opening. I use this for our church worship service, so it isn’t fun waiting for it to open.
Please! Is there a solution?
Peter Doolittle