How Do You Put an Animation in a Tool?

You're halfway there. You just need to load the animation into the humanoid and then play the animation. I would also recommend using a HopperBin instead of a Tool, as a Tool requires a Handle part to work (unless you've already got a Handle in the tool, in that case just ignore that).

So basically, you make a HopperBin in StarterPack (given if you have a Handle part in the tool or not), and then add this into a LocalScript inisde the HopperBin/Tool:

Tool = script.Parent
local player = game.Players.LocalPlayer
repeat wait() until player.Character ~= nil
local hum = player.Character:WaitForChild("Humanoid")

local animation = Tool.DanceAnim --Change DanceAnim to the name of your animation.
local AnimTrack = hum:LoadAnimation(animation) --Loads the animation into the humanoid.

Tool.Selected:connect(function(mouse) --If you're using a tool, change Selected to Activated, and get rid of the code on the next line. Otherwise, keep this the same.
    mouse.Button1Down(connect(function() --As mentioned above, delete this line if you're using a tool.
        AnimTrack:Play()
    end)
end)

Tool.Deselected:connect(function() --If you're using a tool, change Deselected to Unequipped. Otherwise keep it the same.
    AnimTrack:Stop()
end)

This may or may not work, I have NOT tested this. Tell me if the script doesn't work and I'll do my best to fix it.