Maintenance mode

hello,
I was working on a wordpress site that was previously started by someone other than myself. I ACCIDENTALLY placed the site on maintenance mode and now I cannot figure out how to get out of it. Also once the site went on maintenance mode I was logged out of the editor and now I cannot re-enter the site to turn this function off. I noticed on a few other chats it was suggested that you should access the FTP and delete the maintenance.php file but I am a complete novice so I have no idea what any of this means. Could someone please slowly walk me through the steps of disabling maintenance mode? I am very desperate!