I am guessing you mean upload to iTunes? You just set the default location to dropbox when you installed it. Open iTunes first, then connect the phone and manually do the upload to it. You can probably also change the iTunes settings to be the default program to start when the phone is connected.
it opens and wants me to upload to dropbox... and says I need to buy more space to do so. iPhoto is set to upload directly to my photo library. if i cancel out of the option to upload to dropbox, it appears as if i will be able to upload to iPhoto, but all of the new photos never load for me to do so. This just results in a hang up in the computer and an eventual need to force quit the application. My phone is now full of pictures and I can't take any more photos without deleting something... and I don't want to have to delete my photos.