This needs to be done every Spring, and in the UK this is usually the middle or end of May.
If we look first at this page we will see the normal growth of a candle, and photos have been taken over a period to show the growth. In this case there were five candles at this one position and as explained three were removed leaving three others. This may be reduced to two candles later.
These pines often have "flowers" which appear on the lower part of the candle and this causes problems as they have to be removed, and they can extend the length of the candle. There is no way to prevent this as they often appear after a tree has been repotted, and also appears when nothing has been done to the tree. Check out this page.