Thanks to both of you for your advice. I really appreciate the help and it all made a lot of sense. I gave up, in a way, because even if I positioned one item on the video, it would not completely show up in replay, or would partially show up and then the rest would be revealed. I was working with 5 videos so it may have been a lot to process and I saw a number of preparing the preview messages. Anyway, it seems the proper use of offset, etc. is not very intuitive and, as mentioned, the effects icons did not yield satisfactory results. However, I wondered about whether or not the program was doing what I asked and just was not showing up - when I exported the video, with seeming partial appearing and disappearing elements, the resultant .mp4 played as I had intended. So there may be other issues. I don't think I have any problem with memory, etc. but it seemed to be a large project with many items in the video files section.
One last question. I'm using VP Pro v. 8.34 and I've gotten a message that an upgrade is available. Does that make sense and is that a purchase item or a normal upgrade?
Thanks again for your help. I'm not sure whether I had a real problem with the software or if I was overloading it or my computer.