There is a lot more to producing a video for the internet than just shooting and uploading. If you know you have a hard file size limit, you must use a video editing program to edit the video to a slightly shorter run time by cutting out scenes you don't need. Then you have to re-compress the video using a compression setting that will meet the file size requirement.
The other option is to set up your own Youtube channel and post it there. There's no file size limit there. Then you can EMBED the video into your post here.