A Fundoshi a section of thin cotton cloth 2 to 3 meters long depending on your waist. The width is about 10 t0 15 cm, the wider measurement for men. You can make quite a few out of a worn bed sheet. Or, buy light cotton cloth the right length and rip into strips.
Learning to drape and tie them can be done by googling fundoshi images and look for instructions.
I have dressed quite a few lovers in this and they find it very stimulating... especially having a partner put it on.
Try it its fun.