But i can't find that option in AE CC 2015, what does that option called?
that candy lollipop type option is not showing in my AE.
Please please help me
That 'candy lollipop' is called a pickwhip.
It's only visible when you add an expression to property. You add an expression by holding down the Alt/Option key while clicking on the property, or by selecting the property and using the menu to drill down to Animation>Add Expression. In this case the position of the null has been selected.
While the techniques used in this tutorial are pretty good and fairly efficient his teaching style leaves a bit to be desired. You have to look at all online training, especially from enthusiasts and amateurs, with a critical eye and examine the techniques carefully and objectively to make sure they are efficient and effective. Training from Lynda.com or my friend Brian Maffit's Total Training, Adobe TV, My friend Mathias Möhl's Mamoworld, and Video Copilot have been reviewed by professionals and will give you a better foundation. Tutorials for 3rd party effects on the creators websites like Red Giant Software have also been reviewed and generally give you a much better example of efficient and effective techniques for their products.
I hope this helps. Becoming a true proficient takes time and study. Just poking around and experimenting is horribly inefficient. I've been at this since version 1.1 (1993) and I still go through tutorials from known good sources all the time to learn better ways of doing things.