It is good to check with your lama first about your practice.
If you have had a HYT empowerment you can engage in the more extensive sadhanas, such as Wishfulfilling Jewel(a Tharpa publication).
I don't know the requirements to practice the short Sadhana on(the home page of) this web site, I would guess that as it is public on this site, anyone can practice it if they have faith. As you have a Yidam practice i would think it is fine to practice this short sadhana.