After submitting database information there are some issues on the next page.

1) "unknown driver" on the top left corner;
2) There's a totally empty textarea after "Step 2. Adding the code | Please Add the following two lines in your
in the header(before tag)", so I have no clue what to put in the header;

Help please.... :(

To sgmax
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Is your recent post an answer for my question?
I don't understand: you say "... the followig two lines ...", and I see nothing!

To sgmax
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Ok: you wrote about your own problem in the installation, about the lines of code whe have to insert in the "index.php" file of the template!
Sure, it's not easy to know the real place where we have to write these lines.

Is it the cause of my problem?

sgmax said -

1) "unknown driver" on the top left corner;

This error is shown if you have selected a non-supported driver
and this can only be seen in older versions of FreiChatX

Which version are you using ?

2) There's a totally empty textarea after "....

This is because of the previous error.

If you are unable to complete installation even with the latest version
there are two alternatives

1. Quick Installation (will be available in next version only for Joomla)
2. Manually edit code and create tables