"Login failed!"

Hello, my name is Dmitry, I'm from Russia. I've got a problem, perhaps it was already discussed at this forum, so if anything give me a link and remove the topic. I beg you not to throw stones at me ;)
Setting Contao, I tried to log into the admin panel, but on my system is trying to meet me: "Login failed!". I tried to come out of the site, from the pages have become an authorized, but all these attempts were unsuccessful. I tried to go out of accounts k.jones and others, but nothing worked. And all the confusion is that even if I go on the demo page http://demo.contao.org/ and try to log in (through the same k.jones), he gives me an error.
Help me, please!
P.S. I apologize for the bad English. :(

Have you set up the demo (music academy) template in your install?
I think you may be confusing front-end and back-end logins - or your caps lock is on

Try the k.jones login here: http://demo.contao.org/contao

Good Day Everybody
My name is wonze and i am from Cameroon, my problem is that i have downloaded contao CMS from http://www.contao.org , uploaded the unzipped file to my folder in my public_html directory fia an FTP.
In my browser i called the install tool as they adviced http://www.mywebsite.com/contao/install.php
it shows me a window to accept the conditions of the open source, that i did, it directed me to Contao Install Tool
where i entered contao as they say in the installation guide . i done this many times not succeed
Is something wrong? Is there another Installation password? I even try typolight no result.
Please i need help