Without knowing what format iphone5 videos are I suspect you will need to convert the files first to a format which MEP recognises before you can import them to the program. (I don't own any version of the iphone so can't check this.)
So, presuming you have transferred them from your iphone to your computer you need to open each one in a suitable file conversion app. The best I have found is SUPER(c), it is free and can convert almost any video or audio file from one format to another. However, it is not the "easiest" of programs to find on the internet - its own web page, last time I checked, included links to various convertors which are not free - you will need to search on http://www.erightsoft.com/SUPER.html. Just make sure to follow all the instructions to ensure you only download what you want!
Having installed it, decide which format you want the output to be, some type of .avi is perhaps the one MEP will be most happy with (you may need to experiment with precise settings, depending whether your iphone files are SD, HD, 4:3 or 16:9) and then drag one of those files to the SUPER screen and let it convert it.
Please remember: the "instructions" above are very general. Without knowing the precise format of your files it is impossible to be more exact.
Video formats supported: H.264 video up to 1080p, 30 frames per second, High Profile level 4.1 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps per channel, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; Motion JPEG (M-JPEG) up to 35 Mbps, 1280 by 720 pixels, 30 frames per second, audio in ulaw, PCM stereo audio in .avi file format
MEP will support .mp4 and .mov for sure if you have the .mp4 codec activated and .mov if you have the latest version of quicktime installed. .avi is a package format that creates very large file sizes but as mentioned by emmrecs you can pretty much convert any format to any other with the right software tools.
The first thing to determine is what formate your iphone is set to record video at. The easiest way is to copy one of your video files to your PC and look at the file extension of the copied file.
Please note if you are looking to burn video files downloaded from itunes, you are not likely to get MEP to read them as they have all copy protection to prevent you burning them to disc.
Please be very careful using the Super software - see this post here, 5th answer from top, for an experience I had with it earlier this year.
I am also experiencing crashing of my browsers (Firefox, Chrome and IE) trying to access the enright site to check if the additional software disclaimer is still there..