Answer: Upasana lit. means sitting near. That means to say you will be sitting near to the deity mentally. The mind is the media through which one approaches the God. This can be done by repeating the Lord’s name in this particular case the Gayatri Mantra. Timings, fasting, place, rituals etc. are of secondary details. There are books available on Gayatri in our show room at Hyderabad Math. The Swamiji there will also be able to guide you in the matter.