PNG file blurry in After Effects

Your PNG file is blurry because

• it is too small for video and you have scaled it up to fit your comp
• your composition panel is set to half resolution or lower
• the magnification ratio at the bottom left corner of the preview panel is set to 400% or more
• you have enabled Fast Draft in the Fast Previews options at the bottom of the Comp panel
• the layer is 3D and it is closer to the camera than the zoom value effectively scaling the layer up more than 120%

Only the first option, your image is too small is a problem that has to be solved in Photoshop. The other situations are not a problem for your final video, but it may make it harder for you to accurately judge the composition.

If you don't understand everything that I pointed out I strongly suggest you open the Learn workspace or go to the User Guide and study up on how the UI works. 

If you can't solve the problem then we need to see a screenshot that shows the problem PNG file selected in the Project Panel so we can see the footage properties, the PNG layer must be selected in the timeline and the U key pressed twice to show us all of the modified properties in the layer, and the comp panel showing all of the modifiers at the bottom of the frame. Take the screenshot and embed it in the forum using the toolbar in the form and we can help you solve the problem.