Installing Dropbox in Kali

Please go to Dropbox page and download version for Ubuntu (file extension .deb) -- https://www.dropbox.com/install-linux.

This is going to download a file in this format:
dropbox_2015.10.28_amd64.deb

Then run:
wget https://www.dropbox.com/download?dl=packages/ubuntu/dropbox_2015.10.28_amd64.deb

After that:
sudo dpkg -i <package name>

Example package name:
download?dl=packages%2Fubuntu%2Fdropbox_2015.10.28_amd64.deb

Therefore:
sudo dpkg -i download?dl=packages%2Fubuntu%2Fdropbox_2015.10.28_amd64.deb

This will install the package.

For checking the GUI version of Dropbox just installed, please go to Usual Applications > Internet > and see the Dropbox appearing in there.