Module B involves the certification of your products design. This is just a pre-assessment as the product is not on the market yet. It must still be produced. Under CE marking you also have obligations under the production phase of the product and this is what Module C covers.
There are no specific obligations other than that you must take all required steps to ensure the product complies with the technical design that was certified (its the same). Its up to you as a manufacturer to decide how to do this.
We can support with setting a quality system that satisfies the common requirements of good manufacturing practice so you are sure of Module C compliance.