You can do this a few ways.
have a totally unmanned drop point with shares in coolers that you pick up a few hours after drop off. Lots can go wrong with scenario including people who are not members of the CSA taking shares
Have a person who works at the business and is a CSA member man the drop point. This person would get a discounted share and would be responsible for making sure the right people get the shares, collects any bags/boxes dropped off by members and answers questions
You man the drop point