my ipod nano wont let me download video i downloaded off of my computer

Were you able to add the videos to iTunes?

I have the same problem my nano wont take videos that are even on my itunes acount

Not all video format downloaded from iTunes is compatible with ipod nano. Make sure that the file extnesion is mp4 or any quicktime formats. If not, create a version on these format using iTunes or convert using a third party software. Cheers!

How do you convert them in iTunes?

Try to right click the file and select "create ipod version". If this option is gray/unselectable, try the third party converter. Cheers!