Love the design!

Currently I am using the free version and have run across issues with the home page slider. What is the best size for the images to be used for the home page slider? When I first downloaded the program last week, the images auto adjusted to the proper size. Yesterday, the slider totally disappeared and appeared an image of a motorcycle in it’s place. Today, I disabled, then enabled the slider image and it reappeared; but now the images are actual size and not adjusted to fit slider.