As said it needs to be 80x80 pixels, but it also needs to be less than 9.77kb in size.
Imagine a picture as a grid of 80 by 80 squares. If each square could be black or white then you would need 80 x 80 bits (a bit is an on or an off / a 0 or a 1) to store the image. The problem is that in most images each square can be 1 of 16 million colours. So each square in a default image needs 24 bits. So in your 80 x 80 image you multiply that by 24 bits (80 x 80 x 24 = 153,600 bits which is 150kb) "k" is x1024 in binary.
So as well as reducing the dimensions of your photo, you also need to reduce the number of colours. 24 bit colour is "True Colour" (16 million colours per square), 16 bit colour is "High Colour" (or 4096 colours per square) or 8 bit colour gives you 256 colours per square.
Reducing your image to 16 bit colour will be 80 x 80 x 16 = 102,400 bits / 1024 = 100kb (still too large)
Reducing your image to 8 bit colour will be 80 x 80 x 8 = 51,200 bits / 1024 = 50kb
If you still can't face it, send me a PM, I'll give you my email address, send me the image and I'll do it for you.