You can add new shapes by clicking on the bottom left button "Add" and selecting a shape from there (e.g. a "Cube").
You can select and deselect object by clicking on them. Actions only apply to objects that have been selected.
Tools "Move", "Stretch" and "Rotate" can be selected from the bottom right. The "Move" tool is preselected by default.
The camera can be moved around by swiping the screen with your finger or moving the mouse holding down the left mouse button when using the desktop web browser version. You can zoom in the camera by pinching your fingers on the screen or using the scroll button on your mouse. To change the camera?s focus, swipe the screen with three fingers or hold down the right mouse button while moving the mouse.
Move the active object(s) over the passive object(s) and press "cut", the passive object(s) will be cut by the active object(s)