How would I Tween a Frame with MouseIdle?

I don't believe there is a MouseIdle() event, or atleast I don't see one. Feel free to enlighten me if there is with a link to the wiki. Back to your problem, I assume you want to tween the frame when the mouse enters the frame so try this:

Put a local script inside of the frame then for the scripting follow the below code and undertsand it don't just copy and paste.

code:

function changeSize()
    script.Parent:TweenSize(insert the size you want it to change to)
    --you can tween position or size whichever you want
end

script.Parent.MouseEnter:Connect(changeSize)

Now what this code does is it changes the size of the frame when the mouse enters the frame. You're question was not completely clear so this is the best explanation I can provide. If you have more details I can help you further!