Type the name of the power into the box and click "Click to Create". Try to name the page something that will explain what the power set is for. Like "Astral Projection" or "Shadow Travel".
These are the powers that have been made so far that would fit under characters relating to The Shadowhunter Chronicles. Feel free to help out and make some. If you want to look at the full list of powers made so far go to Powers Help/Powers List to see if the power you are creating has already been made or not. Please try to be reasonably canon with the powers and not absurd.