As of now FormGet contact form is completely free upto 300 entries, After that you can upgrade to pro version of the plugin.
It's a common process over internet that you need a account to use the any service you like. After creating form on FormGet when you hit the save button, It ask you to make the account and once your account is created, Your form will automatically save to the admin panel and you can integrate the form on any website you like.
Plugin is extremely easy to use and you will surely love to use it, once you get familiar with it.
If you need any help, Do let me know.
Tutorial link: http://wordpress.org/plugins/formget-contact-form/screenshots/