Before cleaning, vacum the curtains to remove loose dust.
Carefully take your curtains down removing all the hooks and rings.
Ensure you have checked for colour fastness before washing by testing a small area on the back of the hem.
Due to the amount of fabric you are cleaning, a bathtub can be an ideal location for hand washing.
Using a mild detergent and gentle wash the fabric without soaking, rubbing or wringing.
To dry the curtains the best way is to hang them by their hooks in a shade on a strong line.
Once dry and if the fabric allows you can iron the curtains on the fabric side on a warm setting.
Or just hang them back in place.
The weight of the curtains will help any creases to naturally come out.