First, you must get your Setster code ready. Login into your Setster account and select the "Get Widget" tab.  Once there, select the type of widget you want, and customize it's placement and wording. More info on this found here.

Copy the code to your clipboard and now let's add it to your website.

1. In your Joomla site, go to the page HTML editor
2. Paste the code right before the /head section. (optimum location but you can opt to try another)
3. Save your page and publish.