When in the AdBuilder, you'll see your toolbar at the top of the canvas:

On the left most side of the toolbar is your design name. By default, new designs are named New Design. To rename it, double click on the design name and type in your new design name:

In order to undo or redo a past action, click Undo or Redo

The visual grid is useful for aligning certain assets within your artboard. To turn this on, select the Grid icon

The Text tool can be used to quickly add new text to the canvas, including templated text. You can access the Text tool by clicking on it or pressing T as a hotkey

You have the option to save your created text to your asset library by toggling Save To Library before adding. Doing so creates a universal, reusable text asset that can be accessed without retyping.

You can quickly add basic shapes such as squares, triangles, circles and lines using the Shapes tool

You can quickly change the placement size of your canvas by selecting the dropdown of the placement size. More about Placements here