How do I add charges to a person that isn’t connected to a horse as a Responsible Party in the show?

From the Main menu, choose Financial and Maintain Charges. You can find any person and add charges to them for the working show. If the person isn’t connected to a horse as a responsible party already, you’ll see a message telling you that so you don’t accidently add charges to someone who you don’t want to have them. You can then add whatever charges you wish.