Get the location of the latest build from http://www.sublimetext.com/3, download it and install it (this is on Ubuntu):

wget http://c758482.r82.cf2.rackcdn.com/sublime-text_build-3047_i386.deb
sudo dpkg -i sublime-text_build-3047_i386.deb

Now setup Package Manager:

cd ~/.config/sublime-text-3 (or wherever your config files are stored)
cd Packages/
git clone https://github.com/wbond/sublime_package_control.git "Package Control"
cd "Package Control"
git checkout python3

and restart

Install Soda theme:

cd ~/.config/sublime-text-3 (or wherever your config files are stored)
cd Packages/
git clone https://github.com/buymeasoda/soda-theme/ 'Theme - Soda'
cd 'Theme - Soda'

and enable the theme - go to User Settings Preferences file Sublime Text -> Preferences -> Settings - User, and add (or update) your theme entry to be "theme": "Soda Light 3.sublime-theme" or "theme": "Soda Dark 3.sublime-theme":

{
    "theme": "Soda Light 3.sublime-theme"
}

More info:

http://wesbos.com/migrating-to-sublime-text-3/
http://wbond.net/sublime_packages/package_control/installation#ST3
http://www.slashgeek.net/2013/02/11/sublime-text-packages-and-themes/
http://harrywolff.com/upgrading-to-sublime-text-3/