What is a social media authorization workflow?

In our application, we provide a user authentication option that gives him additional rights and functions. Now we need to add the ability to log into our application using social networks (Facebook, Twitter, Google+, LinkedIn). We do not need any of the functions of these networks. I read these articles about social media authentication on Android:

• LinkedId
• Facebook
• Google+
• Twitter

All of these networks provide their own Android libraries that handle the authentication process. I don't know if I need to use them (they have different APIs and seem to be quite "heavy"). I also found a 3d party library that handles all the networking needed.

Now I don't know:

• After a user logs into any of these networks using the respective library mentioned above, what do I need to send to our server to enter our application? Is it an OAuth token (but it looks like it's only valid for the mobile app that uses it), SN user ID, email address, or something else (you can call it an access token )?
• After the access token is sent to the server, which server is related to it? For example, successful authorization aftet through any SN user tries to use one of the functions provided by our login application. Each of these functions requires a server request. So when one of these requests arrives at our server, we need to check if the access token is valid, or should it just create our user instance as soon as the token arrives the first time, and later it is no longer needed?
• Do I need to store the access token locally on the device or after sending it to the server, I can forget about it?
• How to provide a logout function?

Okay, I understand that this question may not be phrased correctly, so please feel free to ask for more information if you need it.