Saddle off, saddle bracket removed, disc out. Put the new one in and reassemble in reverse order

.
The

is an M12 internal Torx screw, but the washer should be 282mm instead of 280mm.
The brackets should be fastened with M8 screws.
Screw into/onto the washer is an M6

.
The brake caliper bracket should always be removed, as this allows you to clean it better, including the mounting for the stones, using a vise. }