I need to make a walk speed change script that changes the walkspeed as the number of wins change?

I am going to assume you have already made a DataStore that gives each player their "Wins". But if you didn't, first type this into a server script (It's not a DataStore, just something that shows a players wins, basically it won't save the players wins):

game.Players.PlayerAdded:Connect(function(player)
    local leaderstats = Instance.new("Folder")
    leaderstats.Name = "leaderstats"
    leaderstats.Parent = player

    local wins = Instance.new("IntValue")
    wins.Name = "Wins"
    wins.Parent = leaderstats
end)

After you are done with that, insert a LOCAL script into StarterPlayerScripts. You should find it under StarterPlayer. After you insert that, do this, assuming each player is going to get one win at a time:

local player = game.Players.LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")
local wins = player.leaderstats.Wins -- Change Wins to whatever you named the IntValue
local value = 10 -- Put whatever number you want

wins.Changed:Connect(function()
    humanoid.WalkSpeed = humanoid.WalkSpeed + value --Or multiply, depending on how intense you want it to be
end)

This is a very simple way to do it. How you reward players' a win is up to you, but the local script should be able to detect that the player gained a win. If you're looking for something a bit more complex than this, let me know.

You can use loop to set the walkspeed of the player equal to their wins value, here is the example! Must be a local script

local plr = game.Players.LocalPlayer

while wait() do
       local char = plr.Character or plr.CharacterAdded:Wait()
       char.Humanoid.WalkSpeed = (plr.leaderstats.Wins.Value) + 16 -- If player wins is 0, the game will still set the player to their normal speed!
end

You can get more resource here :

Goodluck!

( If the link didnt showing up, try this : http://developer.roblox.com/en-us/articles/Loops )