Firstly you'll need a tool allowing you to translate .po file into your language.

You can use Poedit app, or CodeStyling  WordPress Plugin.
http://www.poedit.net/
http://www.code-styling.de/english/development/wordpress-plugin-codestyling-localization-en

After you unzip the archive verbo-premium.zip  you must have folder "verbo-premium" with theme files.

After this go to treeson/media/ln/ here you can see file en_US.po. Now here create new file,

for example fr_FR.po and copy content from en_US.po to fr_FR.po ( to copy content use sample text editor ).

After open fr_FR.po ( using poeditor ) and start translating each word to your language.

After you finished, click button "Save Catalog", and it will create a new .mo file in the same folder.

Then you'll need to open wp-config.php file from the root folder of your WordPress install, and replace this line:

define ('WPLANG', '');

with something like:

define ('WPLANG', 'fr_FR');

Then make sure that .mo file from treeson_/media/ln/ folder of our theme has the same name as your language code: "fr_FR.mo"

IMPORTANT: Is need by one .po file for each language, in case you want to use plugin mqTranslate to enable more languages.

More information you can find here: http://www.catswhocode.com/blog/how-to-make-a-translatable-wordpress-theme