Fitting a water filter for the first time:
If presently your kitchens tap ware come out of the wall. To provide a simple connection for your under sink water filter you must gain access to the cold feed pipe by opening up the wall under the sink. Once this is done you are either in a position where you can place a filter needle valve tap fitting directly onto a copper pipe or if poly cut a tee in and take off a wingback to take an inline ball fix valve and a small water filter adaptor from ½-inch (15 mm) down to the filter tube small bore size given with the kit. If you find you have a galv pipe you will have to use two repair couplings and bridge the gap in between the barrel nipples with poly adaptors and a tee and a wingback followed by the inline ball fix valve and small filter supplied adaptor fitting.
In many ways it is sometimes best to consider a dual pronged attack of placing in a new filter by changing the piping over and installing a bench mounted tap.
If you already have a bench mounted tap then get underneath it and taking a very short flexi hose fit in a brass ½-inch (15 mm) tee into the line and provide another very short flexi hose to take the ball fix valve and filter adaptor fitting on its end.
Next mount the water filter itself and drill out the ½-inch (15 mm) hole in the bench top for the water filter tap. Then simply connect the small-bore tubing with the kit you purchased and turn on the water and test.