you are using the wrong input, use file instead, if you want the button to loke like the circle in your code demo you will need to use CSS to change the way "submit" looks like. This has to be in a form:
<form action="upload_file.php" method="post" enctype="multipart/form-data">
<input type="file" name="myfile"/>
<input type="submit" class="circle-btn"/>
<form>
I don't know what language are you using in the server-side (PHP, ASP.NET, etc) but you will need to create a page (for xample "upload_file.php" for php). You can easily find examples in google about how to create a page like that, just copy pasete the code:
An example in PHP: http://www.w3schools.com/php/php_file_upload.asp
Hope it helps :)