I have a green screen png sequence for trees and want to import this image sequence into Cycles on a plane. It's very simple but I am looking for answer but cannot find.
First, convert it to a video. You can do this with FFmpeg or a similar tool.
Then drag and drop it into a UV/Image Editor. This will get it into Blender.
Add an image texture node to your material. You will need to open a Node Editor, go to the Object Material section (the ball and the cube on the two tab bars in the header), and make sure your material is using nodes (the Use Nodes checkbox, or from the material section in the Properties panel).
Select your video in the node's pop-up.
Connect the Color output to the Color input on the Diffuse BSDF node.
Enjoy! (Hit ⌥ Alt+A to see it in action.)
I haven't actually tested this, but it should work.
In your User Preferences, turn on the included addon Import Images as Planes, and with Cycles as your renderer choose to add an image plane from the first image in your sequence. In the lower left settings when choosing the image, check the box to 'Use Alpha' and confirm. Once you have the image plane, open a node editor and change the Single Image' to 'Image Sequence', and make sure to choose Cyclic. Here I have an image sequence of ten frames that plays when I press play on the timeline.