Most Wordpress installations have a "login" link on the front page of the website. If you don't see the link it's very simple to get there by simply typing in the url field (top of your web browser's)
if your wordpress website is on http://www.mysiteHERE.com then simply add /wp-admin to get to the admin login screen.
your full url should read http://www.mysiteHERE.com/wp-admin
If you have any questions let us know!