To assure the appropriate how to, please tell us what version of Premiere Elements and what computer operating system?
To avoid this type of up side down video import problem in the future, what are the properties of the video that you are importing into your project up side down?
What is the brand/model/settings of the camera that recorded the video?
If the video is coming from a cell phone, you may run into problem with the audio video sync.
Please consider, supply more details, and then we can discuss this based on the details in your reply.