Omegalight27 Hi Omegalight! I'd recommend checking out the scripting reference page in the official docs:
https://rpginabox.com/docs/doku.php?id=scripting_reference
The Add Party Member function found in the functions list is used to add a character to your party. As for referencing an added party member, the "Party Variables" section provides the syntax for grabbing a party member by ID (e.g. to give them items, adjust their stats and properties, etc.)
For example, this grabs the party member having member ID "xyz":
party.member[“xyz”]
Hopefully that helps!