The cold method is easiest as it allows for more transition during placement. By placing the wrap directly onto your nail prior to heating it, you can be sure that you have placed it exactly where you want it without worrying about the temperature.
If you find that you don’t like where the wrap is placed, you could either reposition it prior to heating (before pressing it down), or reheat and reposition.
An alternative warm method to placing wraps cold is to heat them first. Heating the wrap prior to placing it makes it more flexible and easier to press the first time. Whatever works for you is the method you should use. Try them both!