Lots of details missing to help. Please let us know....
1. Are you still working on Premiere Elements 11 Window 7 or 8 64 bit computer?
2. If you are using iPhone 5 video, what are you using
a. Camera 1080p30
b. FaceTime 720p30
and what did you set as the project preset for this project so that the project preset matches the properties of the source media?
3. You mention what seems to be an Adobe Flash Video export...
Publish+Share/Computer/Adobe Flash Video
with preset = F4V - HD 720p (Flash 9 and Higher)
That preset uses as default 1280 x 720 frame size and frame rate = Same As Source.
4. In view of all that, how did you arrive at
I uploaded it to YouTube and then discovered that it was in 360p
Where are you see this "360p"? From the way this is written, you uploaded your F4V file exported from Premiere Elements 11 Windows to YouTube at the YouTube web site. Why did you select the Adobe Flash Video for this task?
5. Please consider
a. project set up with project preset to match the properties of what you have
b. if you want to upload a file to YouTube at the YouTube web site, look at
Publish+Share/Computer/AVCHD with preset of YouTube Widescreen HD. That will get you a H.264.mp4 file (1280 x 720 at 29.97 progressive frames per second). If you want 1920 x 1080 at 29.97 progressive frames per second, then go under the Advanced Button of the preset and customize the settings.
We will be watching for your results.