The first question is are you using the correct ftp user? Go to the manage domains page in the panel and look at the web hosting column for your domain, it will say fully hosted, User: followed by a user name.
Log into FTP with that user name, and you should see a directory named the same as your domain. Click into that directory and you should begin to see your WP stuff.
make sure the setting in your ftp is set to show hidden files.
In that directory check to see if a file exists named .htaccess if it does download it and add those lines to it, probably at the top should be fine. put the file back on the server. If there is no .htaccess make one with those lines. With some ftp clients you might need to name it htaccess.txt to upload it then you can right click and rename to .htaccess
Also if your going to run a secure site, I would disable FTP in the panel, and use SFTP instead.