You use one of the SHARE options to export to the file type you select
The Tutorial Links Page http://forums.adobe.com/thread/1275830 has links to several different share options, starting at link #6
Premiere Elements FAQ List (2 pages of FAQ as of September 2013) http://forums.adobe.com/community/premiere_elements/premiere_elements_faq?view=all
Premiere Elements TIPS List (6 pages of Tips as of September 2013) http://forums.adobe.com/community/premiere_elements/premiere_elements_tips?view=all
What computer operating system is your Premiere Elements 10 running on?
Could you please qualify your question?
Are you asking how to export a video from Premiere Elements 10 and in what format?
Have you already exported your Timeline to a file saved to the computer hard drive and have found that the file size is too large for your purposes? Consequently, your question would be how do I get an export with a smaller file size.
Whatever the case, more details would be needed related to
a. Properties of what you have imported to the Timeline
b. Your intended export for viewing
Depending on the above answers, do you still have the project.prel that was involved in this project and the media that went into it in their hard drive save location (same location as when you saved/closed the project)?