To change the position of items, you can re-arrange the product buttons by sliding them around the screen. To start :
Step 1 : Tap on the pencil icon on the top right.
*Note* Items cannot be moved between categories.
Step 2 : The product buttons will start to jiggle and you can move them around by dragging them. Hold your finger on the item you want to move and slide it to the position you want.
Step 3 : Tap on the check mark icon on the top right to set your arrangement.