To add the login / register widget to sidebars add the widget from Widgets – to your selected sidebar.

Starting 1.15.4  to enable social login in register form enable this option from theme options – Social and Contact as in below screenshot.

The widget looks like this for non logged in users:

And like this for registered users:

Read here how to use all register and login options:

http://help.wprentals.org/2016/08/02/register-and-login-options/