By default, Guide Builder uses the Cobalt Standard form guide layout, but you can select any of the available layouts for your form guide.
You can also add a custom component library created in Flex™ Builder™. A custom library is a Flex Builder SWC file that contains one or more guide and panel layouts. Advanced developers can use Flex Builder to create custom form guide layouts, panel layouts, and controls. Flex Builder is an open-source integrated development environment (IDE) built on the Eclipse workbench.
1.
Make sure Guide Builder is running in expanded view, and select Edit Guide if it is not already selected.
See also 

To select a form guide layout