If you are using credits(entrance) animation, you must put everything within
the slide to allow the text to scroll from below to top.
If you have many paragraph, there are several ways to go about it. One way
is to separate the paragraphs(lets say 5 paragraphs, one textbox). Now, you
will have two textbox.
Have them all within the slide and overlapping each other. Then, add credits
animation on both the textbox, with the second one as "After Previous".
Alternately, you can have make many slides, with all the textbox having
Then, go to Slide Show > Slide Transition. Under Advance slide, uncheck on
mouse click and put a checkmark on Advance slide(00:00) for those slides that
have the credits animation. This is to allow easy editing at a later time.
PowerPoint Heaven - The Power to Animate
Contains tutorials on creating amazing animations for your PowerPoint