MotoPress Layout Editor is a professional plugin for developers. It enables to build and edit the layout of a WordPress theme.
As MotoPress plugin follows GPL and all WordPress guidelines it is absolutely free, the only requirement to install the plugin is that your WordPress theme should be made specially for MotoPress. Look at the Documentation how to change the default WP to MotoPress theme.
You'll find 'MotoPress' in your WordPress admin panel.
For basic usage you may also look over the MotoPress homepage