Simples!
I presume you didnt to the previous work your self ... but if you pop the cambelt cover off, remove the spark plugs (ideally) turn the engine over using the top bolt (Only do this clockwise) to line up the OT Mark on the camshaft pulley with the little mark/arrow on the rocker cover, that will line the engine up, remove the dizzy cap, ensure the rotor arm is pointing at the mark on the distributor body its self, if it is... go a head and unbolt the 13mm nut that clamps the dizzy down, be warned they can get well and truly stuck in there, use a chissel and hammer on the base flange if it is, it will come with a clout. Put the new dizzy on, rotate to ensure the rotor arm is lined up with the mark on the new dizzy and double check the OT mark is still lined up, If it is, nip the 13mm bolt down, refitt the cambelt cover, and spark plugs if you did remove them (helps turn the engine over) and give it a go! If it no longer revs above 5000 RPM you didnt line it up correctly.
hint: note the position of the old dizzy, it will give you a rough idea of where the new one will need to be positioned. but dont rely just by eye.
hint: You can also find the "OT" by removing the green plug on the gearbox, if the lines are pointing to each other, you know its at Top dead centre
