It's pretty easy to do, as there are instructions that come with the rail and element that detail exactly how to do it.  I've done three of these now, one in the old house, two in the new house, and there's very little skill needed.  You just fit the supplied blanking plugs (which have O ring seals, so don't are easy to fit and seal) to one of the top pipe connections and one of the bottom connections (ideally diagonally opposite).  You then fit the heating element into the remaining bottom conn