One more question.
I save it in the Custom tab, and then Animation-->Motion? Or do I have to save it in another section of CTA4? Thanks in advance
Yes, you save in Custom > Animation > Motion in CTA4.
Then you can right click the thumbnail in your CTA4 Content Manager and choose "Find File". This will then open at the location of the motion file, which you can then drag into CTA5 and save in your custom library there.