download the plugin again, delete the existing one after disabling it. Upload the plugin, enable in your admin panel, then Write Page. In this write box you should see a button called Contact or Contact Form amongst Blockquote and others. Press it once and it adds the tag.
Ensure your htaccess can be written to.
View the page, does it display? If yes, then go to the plugin file for the contact form, and cut and paste the CSS only, paste this into your style.css for your theme and edit it. Or you can modify the css within the plugin file.