It’s a nice simple tool to design custom design for your blog. You don’t need any html to play with this, but you need to have an idea of how your final template should look. Working with the tool is easy. First select the layout you like for the template, there are different options available like 2 column, 3 column, left sidebar, right sidebars etc. Once you select the layput just click on each element to change its properties. When you click on an element the properties of the element will show up on the top, enter appropriate values for the fields and you are good to go with a nice custom template.
See the video below to see how it works. Help section is available if you are stuck in between.