First, please be sure you have installed and activated Contact Form 7 plugin, the plugin you can download here:
or you can find it in the downloaded package, plugins folder.
If the plugin has been installed correctly you should see the Contact tab in the left column. Click on it.
To add a new Contact Form click Add New button link
In the field form input your HTML, or use the default, you can also use the tags drop down to add the fields you want