so if we have a bunch of new characters in one mod， what should we do with that

In README/character-mods.txt you'll find the following description

In data.lua:

-- Define character properties
IROBOT = require("__CharacterModHelper__.common")("IRobot")

IROBOT.character                        = { name = "IRobot_character_skin" }
IROBOT.corpse                           = { name = IROBOT.character.name.."-corpse" }

…

-- Create character
local character = table.deepcopy(data.raw["character"]["character"])
CharModHelper.apply_properties(character, IROBOT.character)
data:extend({character})

-- Create corpse
local corpse = table.deepcopy(data.raw["character-corpse"]["character-corpse"])
CharModHelper.apply_properties(corpse, IROBOT.corpse)
data:extend({corpse})


In data-final-fixes.lua:

-- Keep or overwrite the default prototypes?                   --
CharModHelper.check_my_prototypes(IROBOT)

If you have multiple characters, the easiest way is to add more levels to the table and loop over them.

In data.lua:

-- Define character properties
IROBOT = require("__CharacterModHelper__.common")("IRobot")
IROBOT.skins = {}

IROBOT.skins.name1 = {}
IROBOT.skins.name1.character       = { name = "IRobot_character_skin" },
IROBOT.skins.name1.corpse          = { name = IROBOT.skins.name1.character.name.."-corpse" }

IROBOT.skins.name2 = {}
IROBOT.skins.name2.character       = { name = "second_character_skin" },
IROBOT.skins.name2.corpse          = { name = IROBOT.skins.name2.character.name.."-corpse" }

…

-- Create prototypes
local character, corpse

for name, prototypes in pairs(IROBOT.skins) do
  character = table.deepcopy(data.raw["character"]["character"])
  corpse = table.deepcopy(data.raw["character-corpse"]["character-corpse"])

  CharModHelper.apply_properties(character, prototypes.character)
  CharModHelper.apply_properties(character, prototypes.corpse)

  data:extend({character, corpse})
end

In data-final-fixes.lua:

-- Keep or overwrite the default prototypes?                   --
for name, prototypes in pairs(IROBOT.skins) do
  CharModHelper.check_my_prototypes(prototypes)
end

а можно обьеснить для не знакомых с программированием людей?

Sorry, my Russian is not good enough for this. Google translated this as "Can you be visible for people who are not familiar with people's programming?", but that doesn't really make sense. If you want a better explanation, unpack the mod and look at the files in the README folder. Does that help, or did you mean something different?