Walter, please specify what kind of error have you got when you were following the steps of the instruction ?
We suggested you that solution because adding the sign-in and registration forms code just into the Custom text/HTML widget will not work. There is the smarty component
{component class="BASE_CMP_SignIn" ajax="1"} which is outputs the Sign-in box. This smarty component can not be processed within the Custom text/HTML widget.
So you need to create a custom landing page, add it to the /theme_name/master_pages/ folder and then you be able to add this sign-in smarty component on that page. See more information here:
http://www.oxwall.org/forum/topic/29859 .
Or we can suggest you to create the Join page similar to the Facebook Join page and then customize it according to your requests. In this case you can use these plugins:
http://www.oxwall.org/store/item/601
http://www.oxwall.org/store/item/1027
