how to add new SORT BY options?

[bamboozled]

hello

I want to add two options to the drop down product sort menu.

They are to sort by,

NEWLY LISTED
and
SIZE
and maybe
COLOUR

and I would like to delete the sort by A-Z and Z-A options.

I am not sure how to do this and if it will work in the same way that
it works for 'highest price' and 'lowest price'

The site is http://www.rennart.co.uk/shop

thanks