first step.. visit manage domains in the panel and make sure you are using the correct ftp user. Look at the line for the domain and scan over to the web hosting column, there should be a "user" there, you MUST log in with that user.
Once there you should see a directory named YOURDOMAINNAME.COM switch into that directory.
Now if you put a folder name after the / when you filed in the form for the one click, you should see that folder name here. Click into it and you are there. If you left that spot blank on the one-click, then you should already be to your wordpress files and directories.