What computer operating system is your Premiere Elements 10 running on? Are you in a NTSC or PAL setup? I will assume NTSC setup.
When you open a new Premiere Elements 12 project, the project stands with the default project preset 1080i30
Full HD 1080i30
The Adobe design is for the project to set automatically the project preset to match the properties of the import based on the properties
of the first video file that is dragged to the Expert workspace Timeline. In a perfect world, if your video is 1920 x 1080p30, then the project
settings will become
Sometimes the project does it right, sometimes not. When not, then you set the project preset manually (File Menu/New/Project) before you import source media.. See the detail in the following.
According to Adobe, you cannot change the project settings once the project is begun. The answer becomes to start a new project with the right project preset. But, there is a way under circumstances.
Please review and consider, and then let us know if any of the above addresses your question and concerns.