Where to place code for Facebook & Twitter in functions.php

Hi!

We have downloaded a new theme, TwentyTen Lifestyle 1.1, and have some troubles with adding social sharing buttons. We would like to add buttons for both Facebook and Twitter in the gray bar (that contains categories and comments) below each post. The theme only has a functions.php file and every tutorial we’ve found says that you should post the codes in the single.php file.

Where should we post the codes for the Facebook and Twitter buttons in the functions.php if we want them to appear in that gray bar?

Here is a link to our entire functions.php: http://pastebin.com/yF9dYrB7

And this is what our blog looks like at the moment: http://heartcore.se/wordpress/

Any help would be much appreciated! We have tried to tamper with php codes before and ruined everything so this time we don’t dare to touch the php codes if we aren’t certain about what we’re doing.

/Therése & Sofia