What computer operating system is your Premiere Elements 12 running on?
You have not supplied enough details for us to help you. Here is what we would like to know
1. What are the properties of your source video?
Interlaced or Progressive
Pixel Aspect Ratio
We could point you to video properties readout program(s) such as MediaInfo to get that information. But, sometimes we can get enough information just by knowing the brand/model/settings of the camera that recorded that video.
2. What is the project preset that you (manually) or the program is setting automatically? If you do not know, then go to Expert workspace Edit Menu/Project Settings/General and tell us what readings you see for Editing Mode, Timebase, Frame Size, and Pixel Aspect Ratio, even if those fields look grayed out.
3. When you are playing back you Timeline content in the Edit area monitor before export, what is the quality of the video audio play back? Pixelated? And, what are the details of your export under Publish+Share/?
Lots more questions, but let us pause here and rule in or out the project settings being the prime factor for the Premiere Elements problem that you describe. Please do not hesitate to ask questions and to ask for clarification on anything written.