Q: how do i download a .ppt (powerpoint presentation) to my iPad ?

Do you have Powerpoint on your iPad? If you do you can access it from the cloud. If not email it to yourself.

E-mailing is the easiest. If the file is too large to e-mail (most mail providers top out at 25 meg or less) then you could look into something like dropbox or onedrive or anther cloud based service. Upload it there, download it onto your iPad.