A lot of times people will send over the login to WordPress but not the link to the admin section.

To get into the WordPress admin section of your site just type in your URL of the WordPress site followed by a /wp-admin or /wp-login.php

So an example of this would be:

http://www.yourwebsiteurlhere.com/wp-admin/

or

http://www.yourwebsiteurlhere.com/wp-login.php