Just for background information, what computer operating system is your Premiere Elements 12 running on?
The generalized answer is Add Media/Files and Folders/Projects Assets from where you drag the photo to the Expert view Timeline.
But all that can generate a mountain of questions about the photo and the project into which it will be going
a. what are the pixel dimensions of the photo - will or will I not have to resize or crop/resize the photo for the project
b. is the photo going into a project that will consist of photos and videos
c. if video inclusion, that leads to questions about the properties of the video so that you can set the project preset to match those
d. that leads to questions on the best size to have your photo before you import them into this project.
So, one simple question generates a lot of side questions.
Please let us know how we might help to sort out the details for your Premiere Elements workflow and its source media.
Just drag and Drop on the timeline! This should work straightaway if
1. You have a 64-bit OS OR
2. You have a 32-bit OS and the image resolution (height x width) is less than 16M