How do I add another name onTouched function?

Add an elseif.

local debounce = false

function onTouched(hit)
    if not debounce then
        debounce = true
        if hit.Parent.Name:sub(1,17) == "AFK Noob Lv 1 HP " then -- I want to add different name here, like skeleton 
            hit.Parent.Humanoid.Health = hit.Parent.Humanoid.Health - 25
            wait(0.5)
            debounce = false
        elseif hit.Parent.Name:sub(1,8) == "Skeleton" then
		--// Do stuff
        end
    end
end

script.Parent.Touched:connect(onTouched)

There are better ways to go about doing what you're doing, though. Hope this helped.