Hi Julia,
We don't yet offer a way to put a Google + button in the header (where your Facebook, Twitter and Pinterest buttons reside), but you can put one on your home page in one of the text areas. To do so, first generate your Google + button via this link:
https://developers.google.com/+/web/badge/#configureor, as an alternative, generate a +1 button here:
https://developers.google.com/+/web/+1button/Once you've followed Google's instructions and copied the code you need, go to the "Home Page Text" link in your CraftLaunch control panel. In one of the text boxes, switch from regular to HTML mode by clicking the "Source" button in the toolbar. Then paste the code into the text box where you'd like the button to appear (if you're not comfortable with HTML, just paste it in the bottom of the box). Click "Update" and you should be all set!
If you need more help with this, please feel free to post on help.craftlaunch.com--you'll get a faster response there :)
-Scott