Honestly just google "comet stacking tutorial" there are many ways to do it not to mention software types PS there was nothing wrong with your first lot of data from pier 12, just a lack of experience on your behalf as well as you choosing to use a slow F/9 system for only 1 hour of data!

I solved already, it was quite easy in fact. First data had to much bad coulumns so I agree with you up to a point but it doesn't really matter now as I'm happy with different pier and camera. Perhaps I would try another comet pay as you go , on the same pier. What time do you recommend for 19P/Borelly ?