The following video shows you how to animate your slides:
One more case that's not mentioned in the video is when you'd like multiple slide elements to appear together at the same time. For example, let's say you'd like an image and code chunk to come in together, then another image and code chunk to come in together after that. You can do something like this:
plot(mpg ~ hp, data = mtcars)
Both elements in part 1 would appear together, followed by both elements in part 2.
If you have questions, let us know!