Hi,
you can do this by follow these steps:
1) Create php content by creating a file called /plugins/jsn/socialnetwork/app/View/Users/ajax_page.ctp and add to this file the content
2) Create the link in left menu
- Access to Admin Panel (http://docs.easy-profile.com/index.php/article/social-network-configuration)
- Go to Theme Manager
- Choose "SocialNetwork Theme"
- Choose the file to override from left menu (Users->view.ctp)
- Click on button "Copy" and copy it in "Blue Theme" (With this you will create the override, the override will be not re-written wh en you install upgrade of the plugin)
- Come back to Theme Manager and choose "Blue Theme"
- You will see your override to customize.
- In this new file you can add something like this at line 159

<li>

				<a data-url="<?php echo $this->request->base?>/users/ajax_page/<?php echo $user['User']['id']?>" rel="profile-content" href="#"><i class="icon-file-text-alt"></i> <?php echo __('New Page')?></a>

			</li>

3) Create controller function
in file at /plugins/jsn/socialnetwork/app/Controller/UsersController.php you should add a function like this (for example at line 14):

public function ajax_page( $uid = null )

	{

		

	}

NOTE: changes at steps 1 and 2 will be not overridden after upgrade, but unfortunately in future when you upgrade Social Network plugin then you need to re-apply step 3