I bought mine 20 years ago. TRA say it should be body colour, so I sprayed it black. It came as 3 pieces. One left, one right and a small piece that goes over the top of the rad. Mine came with instructions and some brass clips like you would use for holding 3-hole loose leaf pages together. I slid these through the holes provided to make it all into one piece.
You don't need to drill any holes in your TR. Remember that these were an after-thought from S-T about mid 1958 when all the TR3A owners started to complain that they were all having over-heating problems. So they were made cheap and had to be easy for the dealers to install this give-away fix to satisfy the customers.
First you will have to remove your grille. It'll take you less time than normal because you have no bumper. You slide the air deflector into the grille opening and up so that the top is above the rad and fit the two sides close to the sides of the rad. There should be crease lines where you do this along both sides of the rad. Also there should be a crease at the bottoms of both sides, which you bend flat - towards the grille opening. These wedge against the floor of the rad pan. There are two large holes about 1 to 1-1/4" diameter in the side pieces which line up with the holes where normally the upper bumper supports go. Use a bolt and some large flat washers on each side here if you are not going to use the upper bumper supports.
John - I don't have any photos handy and while my deflector is out and sitting on my workbench right now, I feel lazy with all this heat and sunshine.