How do you use a non-localplayer in a script?

Why it's better to do it this way:

Grainless_Bread's answer will work in most cases but this will work as long as Hit is a descendant of the Player whereas his only works if the Character is the immediate Parent of Hit

The Solution:

function getPlayerFromCharacter(descendant)
    for _, Player in pairs(game:GetService("Players"):GetPlayers()) do -- Iterates through a list of all Players
        if descendant:IsDescendantOf(Player.Character) then -- Checks if the Player the for loop is currently at's Character has Hit as a descendant
            return Player -- Returns the Player
        end
    end
end

script.Parent.Touched:Connect(function(Hit)
    local Player = getPlayerFromCharacter(Hit)
    if Player then
        --Insert your code here
    end
end)

Don't forget to mark my answer as the solution and upvote it if it answered your question :)

Here you go

script.Parent.Touched:Connect(function(plr)  -- the plr between the parameters is a part that came in contact with the part.
local player = game:GetService("Players"):GetPlayerFromCharacter(plr.Parent)  

if player then 
    --enter script here

end
end)

Hope this helps

<3