Sorry your having problems with this. Perhaps it would be best to start by trying to get your form working 'as is' - and then look at ways to customise it to your site design once you have a known working copy.
If you are happy to do it in steps like this, it will make it easier to diagnose problems should they occur later on.
So assuming you are starting with a fresh version with the original downloaded files, The following are the steps to take:
1. In your downloaded and unzipped 'ContactForm102.zip' inside the folder 'ContactForm_GMC', open the folder 'WA_Globals'.
2. Using a plain-text editor (such as Notepad or Dreamweaver in code view) open the file 'WA_Globals.php'
3. Find this line:
$WAGLOBAL_Contact_Email_To = "firstname.lastname@example.org" ;
and change the email address between the quote marks to the email address you want the form to send the input to.
That's it for the basic settings. You can make additional changes to the WA_Globals.php as specified in the 'contact_form_sp_globals.pdf' (Subject, CC, BCC etc.) should you wish to later.
Upload all the files from the 'ContactForm_GMC' folder to your server, and then navigate to the 'contactus.php'. Submit a trial form, and post back with what happens. We can then look at your other issues.
EDIT: When you post back, please could say what OS you are using, (Windows, Mac) and what software you are using (Dreamweaver?) and any info that may help with your intended modifications.