Instructions
Start a new game of Forge from the main menu. Choose the level you would like to rearrange as the Guilty Spark.
Press "Up" on the control pad to transform from your Spartan or Elite character into the Guilty Spark Forge Editor. Use the thumb sticks to fly around the level.
Use the "A" button to open the forgeable item menu and select objects. Pressing the "A" button while holding an item drops it onto the map.
Preserve your custom map layout by pressing the "Start" button and selecting the "Save and Exit" option.