I don't know what you're asking for. Are you referring to skewing the image?
You need to learn about anchor points.
Move the anchor point to the edge of the solid-color layer. Then scale the layer.
I very strongly recommend that you start here to learn the basics of After Effects:
That's it. Thank You
Why can't we just drag the side of the solid that we want and then adjust it to suit? Seems like a complete faff to have to change an anchor point and then scale the image. Not to mention that even with the anchor point at the edge of the image both sides still move.
Plus the link you have sent is kinda useful but I don't personally have the time to sit and look through each video until I find the relevant bit about anchor points. Can you direct me, please, to the particular section that mentions anchor points.
Todd no longer works for Adobe.
To answer your question, scaling anything in After Effects scales it from the anchor point - thus the need to move it around depending on your needs. In most cases, you'll want the anchor point in the middle, but in this case, just move it to the edge.
You said that both sides still move if you have the anchor point at the edge. Are you working with a shape layer or a solid?
The link he sent was for an overall training in the basics of working with AE. Since the original poster didn't seem to know how to work with anchor points, there were obviously going to be a large number of other basic things they were missing. If you'd like to know more specifically about anchor points, type anchor point into the search field of the Adobe After Effects help.