What version of Premiere Elements are you using and on what computer operating system is it running?
The within program feature has limits, for more recent versions 2 GB/15 minutes.
a. Upload your content Timeline to YouTube with the YouTube feature in the program. That feature has presets which
are supported by YouTube.
b. If you are going to be exporting your Timeline content to a file which will be uploaded to YouTube at the YouTube web site...you can consider
(example, if you are using Premiere Elements 11, 12, or 13)
with Presets = MP4 H.264 1920 x 1080p30
for lesser default resolution 1280 x 720 Presets = YouTube Widescreen HD.
If you give us some information about the properties of the video you have on your Premiere Elements Timeline and your project preset,
we can fine tune some more details for you.