There's a few options for inserting the social sharing buttons into a Kunena topic. First, please understand that you should not try to add the sharing buttons on a per-post basis. The social networks all count the Like's for a page based on the URL. There will be no good way to have a like count for each post, only for the whole thread.
As for adding the sharing buttons, there are a few options. I'll outline them here, which should help you get started, but if you need any more information on any of them, just let me know.
JFBCSocialShare Module - This module has easy parameters that you can use to configure each of the sharing buttons. Once configured, you can have it show on your Kunena pages in a few ways:
* Floating - This is what we have setup in the bottom right of every page of this site. It's an easy sharing row that is always visible on the page
* Standard - The module can be set to display in any standard module position. Kunena has a few built-in module positions, like:
kunena_topictitle (top of the page)
kunena_profilebox (near the user's profile information)
kunena_msg_1 (directly after the first message. Can use 2,3,4, etc)
kunena_bottom (bottom of the page)
For more information on available module positions (and how to find them on your site), see
www.kunena.org/docs/Module_Positions
Template overrides - If there are no module positions that you like above, you could modify your Kunena template files to add the sharing buttons to any place in the output. This is a little more complex, but more flexible. If you need more info on this, just let me know.
I hope that helps,
Alex