You will have to slice it up using masks or by separating the elements to layers in Photoshop. A PNG is just a solid layer with no intrinsic separate sub-entities that AE could make any sense of. Once that's done, you can move on to all the good stuff like adjusting anchor points and animating your positions and opacity.
I would apply a text animator to the text layer. There is a text animation preset that is called Raining Characters Out that you could start with. This effect randomly causes letters to fall out of frame, changes the letters by applying a character offset and then echoes the letters to give an additional effect. Once you apply the effect select the text layer and press the U key twice to reveal all modified properties. Select the Character Offset text animator and delete it. If you don't want the Echo effect delete that. If you want the letters to fall off in order turn Randomize order off. Adjust the Y value of the Range Selector Position so the letters fall completely off the screen. Adjust the Range Selector Opacity as needed to get the effect you want. Then adjust the position and timing of the Range Selector Offset to get adjust the timing of the letters falling off the screen.
You've just learned how to use text animators. For more instructions on how to use text animators type "animate text" in the Search Help field at the top right corner of AE and check out the community resources. It's a great way to quickly find training on any effect or procedure in AE.
Now that you have the text behaving as you what it to you can animate the position and opacity keyframes to match the timing of the text layer. If you also want to add rotation use the Anchor Point (Pan Behind) tool to move the anchor point of the the other layers to the center of rotation for each layer you want to rotate.
That should get you started.