How to I make the white in my trail transparent instead of opaque??

If you have GIMP you should try using the eraser on it,when you rub it should make it transparent.

How would i do that?

You'll have to download GIMP,just look for the latest version in google.

No, i have it downloaded i just cant erase the white to make it transparent

Hmm,I wonder if its the version you have cause thats what I do and it works fine,I'll check the settings on mine maybe there is one for it.

If you're using GIMP 2 than do the following:

Click on "file" > "New">
> set your resolution [128,256,512] and after that >
> bellow the "width" and the "height" windows it will say
"Advanced options", click on it >
> Than find a text saying " Fill with" and choose your background to be Transparent.
And click "ok".

You can draw anything on it, but the parts that look like a chess table will be transparent.

What extension should i save it as? .jpg, .gif?

jpg

PNG.

It only works as a PNG file.