How do you reference a humanoid?

basically I wanna change an IntValue to a Player's Walkspeed, But I cant seem to reference the player... Can anyone tell me how?

This question was already asked and answered.

https://scriptinghelpers.org/questions/100912/how-to-reference-a-players-humanoid

If it's in a local script, first learn how to get the local player, then the character. Then you can access the humanoid and setup the event to fire whenever the property changes!

There are many ways to reference a humanoid. If you're making a leaderboard script, I assume you have some code that triggers when a player joins the server. From that, you can get the player's character and then their humanoid

Here's a quick example:

game:GetService('Players').PlayerAdded:Connect(function(player)
	local character = player.Character or player.CharacterAdded:Wait()
	local humanoid = character:FindFirstChildOfClass('Humanoid')
	
	local leaderstats = Instance.new('Folder')
	leaderstats.Name = 'leaderstats'
	leaderstats.Parent = player
	
	local speed = Instance.new('IntValue')
	speed.Name = 'Speed'
	speed.Parent = leaderstats
	speed.Value = humanoid.WalkSpeed
end)