1. Before you start, close Sublime Text 3
2. Create a folder in Dropbox called Sublime Text 3
3. Navigate to Sublime Text 3 folder in your Library
cd ~/Library/Application Support/Sublime Text 3/
4. Move the following two folders to this folder.
mv Packages/ ~/Dropbox/Sublime Text 3
mv Installed Packages ~/Dropbox/Sublime Text 3
5. Create symlinks from their original location to their new locations in Dropbox:
ln -s ~/Dropbox/App Settings/Sublime Text 3/Packages ~/Library/Application Support/Sublime Text 3/Packages
ln -s ~/Dropbox/App Settings/Sublime Text 3/Installed Packages ~/Library/Application Support/Sublime Text 3/Installed Packages
5. Open Sublime Text 3 and share this post, thanks.