MarketPress site - how to put a "local pickup" option instead of shipping?

Hi! We have a site that sells candy and the vast majority of the orders are expected to be local folks picking up the candy. We want those orders to go through with free shipping and not have to go through the USPS account or anything. How is this accomplished?

For the smaller subset of orders that will be shipped, we need to calculate shipping by weight through USPS.

Thank you for your help!