1st, you upload from your computer to an internet site, you import video into Premiere Elements
(to reduce confusion see A glossary of video terms - http://www.manifest-tech.com/links/video_terms.htm page)
2nd, what version of Quicktime do you have installed?
3rd, The Elements Tutorial Links Page http://forums.adobe.com/thread/1275830 may also help
4th, IF your video uses a Variable FRAME Rate you may have editing problems
Some people find that Iphone won't edit easily because it uses a variable frame rate
- A possible fix in message #22 http://forums.adobe.com/thread/934466
What version of Premiere Elements are you using on Windows 8.1 64 bit? For now I will assume Premiere Elements 12 in a NTSC set up.
Your iPhone 5s video is expected to be 1080p @ 30 progressive frames per second? Do you confirm that? Because of the source of your video, it is highly likely that you are dealing with a variable frame rate.
Please give the following a try to see if you then have an "importable" product to take into Premiere Elements presumed 12/12.1.
Download and install the free HandBrake program.
Import your video file into the program.
Make sure you browse to and set Destination (suggested Desktop location)
Go to the Video Tab and set
Video codec = H.264 (x264)
Frame Rate = 29.97
put a dot next to Constant for the Frame Rate
Click on the Start at the top left of the workspace
Wait for the "Queue Finished" to appear in the progress bar at the bottom left of the workspace.
Then see if this H.264.mp4 (1920 x 1080 @ 29.97 progressive frames per second file can be imported into Premiere Elements 12 project with a manually set project preset of NTSC/DSLR/1080p/DLSR 1080p30@ 29.97.
Details for setting manual project preset can be found in
The details that I have posted in this reply are customized for Premiere Elements and should work fine for you.
We will be watching for your results.