Once you've created your dashboard, click on the "puzzle-piece" icon to start creating a custom widget:
This will bring you into the widget editor where you can choose the type of visualization you want to start with or you can choose the data-point you want to start with.
The data-points generated by Signals Analytics Engine are shown at the top of the dimensions menu under "Stratifyd", the rest of the data-points from the data-source are below in their respective categories.
When creating a widget, order matters. The first dimension you select will be your primary dimension (usually the x-axis on a graph). From there, the subsequent dimensions will fall into place based on the visualization you select.
Make sure you look at the options, color, font, and style tabs to make further customizations before adding it to your dashboard.