When you require a ModuleScript, it’s run. If it returns a value, then that’s what you get from it.
-- MyModule.lua
return "Hello world!"
local returningValue = require(script.MyModule)
print(returningValue) -- Output: Hello world!
I believe you’re trying to return a table called Main, you can access the table by doing something like this.
local Main = require(script.Handler) -- change this to the path of the 'Handler' module
Now, to integrate it with your script, you’d want to do:
Note: I made the variables local. For more info on that, feel free to check out the DevForum thread here.
local Ascended = game.Workspace.KronosAscended
local Handler = require(Ascended.Main:WaitForChild("KronosHandler"))
game.Players.PlayerAdded:Connect(function(player)
print("PLAYER_ADDED")
Main.AddGui(player)
end)