I'm sure there'll be better instructions from other Dwellars, but the way I did it was to upload the videos to YouTube. It was less an issue of how big they were (from memory - I may be wrong) and more how long they were (maximum 10 minutes)
If you can get that sorted, it's just a case of coming back and embedding the video:
[ youtube ] the numbers after the equal sign [ /youtube ] no spaces.
Hope that gets you started, even if I won't get to see it for months
