First, we recommend 1) replacing the standard Login modules on your page with the SCLogin module and set SCLogin's 'Registration Component' option to K2 or 2) creating a template override for your existing login modules to add the social buttons.
Second, you can also override the K2 registration form to add the Login Easy-tags.
If you want to use the Easy-tags, it should be just as simple as adding the following code.
If you want to customize the buttons further, please look in your backend at Components > JFBConnect > Social > Examples for more options.
The Social Profiles - K2 plugin is for setting up the profile data that will get imported into K2 when logging in via a social network.
I hope this helps clarify how to add the buttons, but please let me know if you have more questions going forward.
-Melissa
How to integrate jfb login with k2 registration
