To set a length of time for each slide, first ensure you know how long you want each slide to be shown to cover the length of the track. Then go to Slide Show >>Rehearsal.
A screen will come up showing you the 1st slide and two times. One the length of the current slide, the other the total time of the presentation.
You can then pause the presentation with the Pause button at the time you want, then click on the Play arrow under the slide to save that time and move on to the next slide. You can also click the Next Slide arrow under the slide and that time will be saved. Do this through the slides and save at the end.
However, although I can find out how to make a track last as long as a slide show ie set it to loop, what I really want to find out is an easy way to make sure the slideshow runs automatically to the length of the track.
Eg is there somewhere where I can set the slides to change at set intervals evenly across a track? (Sort of like setting all columns to the same size across a table width in word iykwim?!)
The only way I can think to do it, but I haven't tried this, is to take the length of the track eg 4:08 and divide it as best I can between the number of slides and then set the slides to last every 5 seconds or something? Can that also be done?