To build a new tool, simply select it from the left menu. You will be directed to a new page containing a list with your existing tools in that category. If you didn't create any tools, the list would be empty.
To create a new tool, simply click on the plus (+) sign at top or the green Create New button at the end. Then you will go to a new page which needs essential information about that tool. After finishing the form simply submit it. When you have returned back, you will see a box containing a code to be used wherever you want. By clicking on that box, the code is copied to the clipboard. Besides you can see your tool preview in the frame below the box. Please consider that since the tools are responsive, they might act differently in a full width window than the preview section.
In the tools listing page, there exists four buttons in front of each tool you have created. The first orange button disables the tool. It can be re-enabled by using this button, too. The second tools direct you to a page with statistical data about that tool. The third blue button allows you to edit and modify your tool; and the final red button completely removes the tool.