By stabilize, he means add potassium metabisulfite (also called kmeta or campden tablets) and potassium sorbate according to the directions on their packages. This will stun the yeast and stop them from reproducing. As you should have allowed you wine to clear first (a couple of rackings or by using a fining agent or filter) the remaining yeast shouldn't be able to metabolize the sugar you add to sweeten your wine to the level you desire.