To move and position an object in your Scene
Make sure you are in the Scene Creator and not the Model Creator
Select the four outward-pointing arrows on the editor toolbar. This will put your object into move mode
Select the item you want to move by clicking on it, or selecting it from the object tree
You will see three arrows which represent the three axis of movement. This widget will be at the pivot point of the object. If you can't see the widgets, click and drag the background to rotate the camera until you can see it.
When you hover over one of the coloured arrows it will turn yellow. This means it is active and you will be moving the object on the arrows axis
Click and drag to move the object back and forth in the chosen direction.
You can also enter specific values in the Transform section on the bottom right of the Properties menu
You will see there are also three coloured flat squares at the centre of the widget. These allow you to move the object in two directions at once as if it was stuck to a flat surface (this is what the square represents).