How to use a Plugin After Sucessfull Installtion?

I have just installed nopCommerce 2.3. But how we can use a plugin. For example, there is no login for Facebook and twitter, although they are installed. I need to now how to add my plugin inside a page.

I also need to add custom Menu Options?

1. Log in as an admin.
2. Select Configuration > External Authentication Methods

You will find the list of installed authentication methods where you can configure them for use on the website.

Thanks. This work.

But, how I can build a Custom Module(like Event Calender, NewsLetter, etc)? Is a plugin appropriate for this? How to show this custom module in a particular page? Is it possible to add a custom Menu option?