Thanks for writing. There are several ways to translate the theme. Personally, I like to use the program Poedit, you can get a copy over here: http://www.poedit.net/

First, download and install Poedit. Then, see that within the theme files there’s a folder named “lang”. Over there you can find the translatable files. So, you’ll need to do the following:

1. Open the file in Poedit.
On the left, there’s a box with the original message (in English) from the POT file. Beside that box is where you add your translation.
2. Go to File → Save as… to save your translations in a PO file. (must be named sv_SE.po and sv_SE.mo)
3. When you are finished translating, go to File → Save as… again to generate the MO file.

Finally, you need to be running your WordPress install in Swedish:
http://codex.wordpress.org/WordPress_in_Your_Language#Swedish_-_Svenska_.28sv_SE.29

Best,
Juan.

Have a nice day,
Juan.