How do spawn in with a skateboard and press e to drop it and ride it?

There is indeed. This is exactly how to:

local skateboards = {}

function skateboards:GiveSkateboard(player, skateboard)
    player.Parent = skateboard
end

game.Workspace.ChildAdded:Connect(function(child)
    if child:FindFirstChild'Humanoid' then
        local p = game:GetService('Players'):FindFirstChild(child.Name)
        if p then
            skateboards:GiveSkateboard(p, nil)
        end
    end
end)

Review:

• In line 1, we create an array of skateboards.
• In line 3, we create a function to give the skateboard.
• In line 7, we set up an event that listens for a child being added.
• In lines 8-10, we check if the child added is a player.
• In line 11, we give players a skateboard. Neat!