Folding your Naginata clothes, called hakama ( black or dark blue pants-skirt) and gi (white shirt). You can also wear a obi (white belt) underneath for better fit. This is usually recommened by your senpai or sensei. How to fold your hakama and gi can be seen in the video below. (The video is in Dutch and has English-generated subtitles which may or may not be translated correctly.)
Folding the hakama https://www.youtube.com/watch?v=gXF2xLsQgwY