I’ll be doing a post soon on my experience of Vajrasattva Ngondro, and thought it would be helpful to provide some background information on tantra. I myself wouldn’t be able to explain it very well, but I would like to provide some helpful resources that could.
One preparation for the Vajrayana (tantric vehicle) is understanding the 3 principles of the path: Renunciation, Bodhichitta, and Wisdom. You can get a great series of audio recordings on the 3 principles of the path from Jamyang Buddhist Center, London. These were taught by Geshe Tashi.