If you’re handwashing your undies:
Apply a little detergent and lightly rub.
Rinse with water until the detergent is washed off and then hang dry.
If you’re machine washing, wash with like colours only. Use of A delicates bag is preferred.
30 to 40 degree Machine wash cycle.
Tumble dry and avoid using softener or extra fragrant detergents!
PS: In any wash type DO NOT USE BLEACH