Updated for 7.0
Click on the Settings icon (the gear) located to the right side of the search bar. This will take you to this page:
Within the horizontal navigation bar select Users. Then, select Costume Sizes. This will take you to this page:
To edit the label of the costume, click the desired box to change the verbiage.
If wanting to remove a size, click the ON button located to the right of the size in question. This will change the button to say OFF.
To rearrange the order of the sizes, click the two arrows icon located to the right of the ON/OFF button. Drag to the desired located.
When done, click the Update button in the bottom right-hand corner.
Removing costume sizes will lose any existing member records of that Costume size.