My frame size is set to 680X480. I need to change my frame size to 1920 X 1020

How did you set the size for your project?

Did you manually select a size when creating your project?

If you want your project to match your video, you only need to create a new project... without setting a frame size... and then drop a video file on the timeline for the program to match your video

That's not a frame size that's available in Premiere Elements.

You can do 1920x1080. But then your 640x480 video won't fill the frame. It will be black on the left and right.

If you want to create a 4:3 video, your only option is 640x480.