If your skirt is transparent, you can consider the following ways to add lining:

1. Underwear lining: You can make it yourself, cut the crotch of the pants of the same color, leaving only the waist and legs.

2. Shorts lining: You can wear a pair of shorts under the skirt, which can not only protect privacy, but also increase the comfort of wearing.

3. Directly add the lining of the skirt: use the cloth of the same color or similar color as the lining and sew it on the inside of the skirt.

It should be noted that when lining, the appropriate lining material and color should be selected according to the specific fabric, and the length and fixing method of the lining material should be paid attention to to to avoid the lining material from being exposed or affecting the wearing effect.