Two ways to handle this:
Comment out the HTML that you do not want to be displayed in the template (see template 'register' in the template manager under your style), and changing the input fields to a hidden type, so when the form is submitted it satisfies the PHP code. (More Advanced method - Allows you to have different styles with different templates using the distributed PHP code).
or
Comment out the HTML you do not want to be displayed in the 'register' template and comment out the PHP code in 'register.php'. (Recommended method for you at this point if your not at an intermediate level in HTML.)
This is something you can do with a bit of trial and error. If you run into trouble, just ask. A little learning of the basics here will go along way. It is why I am not simply just posting the code.
Comment out HTML block using <!-- commented out -->
Comment out PHP block using /* commented out */
Lots of examples on the web on how to comment out code.
I am here if you get into trouble, although almost anyone can help you with this.