Sync with iTunes.
Connect the iPad to the Mac and launch iTunes.
Click on the iPad name on the left side under devices.
Click on the Photos Tab on the right.
Click on all Sync Photos from heading and select from where you want to sync the photos - iPhoto?
Click on the albums, events, faces - or sub folders that you want to include in the sync.
Click on Apply in the lower right corner of iTunes
Another way. You can use a USB flash drive & the camera connection kit.
Plug the USB flash drive into your computer & create a new folder titled DCIM. Then put your movie/photo files into the folder. The files must have a filename with exactly 8 characters long (no spaces) plus the file extension (i.e., my-movie.mov; DSCN0164.jpg).
Now plug the flash drive into the iPad using the camera connection kit. Open the Photos app, the movie/photo files should appear & you can import. (You can not export using the camera connection kit.)
Secrets of the iPad Camera Connection Kit
Another way is to drop the pics into your dropbox, then save to your ipad photlibrary from there. Tedious, but it works. I've had probs with the sync which seems to work sometimes and not others, depending on the weather or the state of the economy or something - perhaps just my incompetence. If you've only one or two pics, dropbox saves having to mess around with iTunes.
Just while I'm here, does anybody have a rational explanation as to why one can't simply copy pics to clipboard and then paste into the DCIM folder on the ipad? Why on earth this convoluted bolloxing about with iTunes?