A. Use the item palette
B. Use player inventory
C. Use the command
/ds shop <shopname> add <item> <value> <median> <stock>
/ds shop <shopname> add <item> <value> <min value> <max value> <median> <stock>
/ds shop <shopname> addhand <value> <median> <stock>
/ds shop <shopname> addhand <value> <min value> <max value> <median> <stock>