Most people know how to wash cotton, but if not here goes …
We recommend washing separately before first use. Wash whites on their own, and use a warm gentle machine wash - 40° is fine. 55° is the temperature at which those infamous dust mites are killed and so won’t harm occasionally. Higher temperatures can damage the yarn. Don’t leave them too long in the machine, and either line dry or warm tumble dry. Warm iron on the reverse.
Don’t bleach and avoid optical brighteners – leave them to paper manufacturers.
Dry cleaning is fine too.