A tulku is the present reincarnation of a previous great master. The Tibetan སྤྲུལ་སྐུ་ means 'emanation body', meaning that the present rebirth is an emanation of awakened mind. They have deliberately chosen to take rebirth out of compassion, to continue to work for the benefit of others.
Once recognized, often at a very young age, tulkus are expected to undergo rigorous study and training. They receive the best education and are expected to rank at the top of their class. They receive instruction from the greatest masters of the day and bring those practices to their culmination.
The tulku has the responsibility of preserving the tradition in which they are said to be the lineage holder, but the way in which they carry out that responsibility depends on the tulku themselves.
They might put their efforts into strengthening the education system.
They might emphasize retreats in which the teachings become a living experience.
They might travel extensively, teaching and inspiring others in their own practice.
They might assist the poor and hungry in their communities.
They might become respected doctors who cure disease.
They might focus on preserving the textual tradition and aiding in translation.
They might disappear and live the life of a wandering nomad, renouncing their high status and reminding others of the importance of actually committing your life to your practice.
The one thing the tulku does not do is wait for permission. They know they have taken on this life to be a living example of the practice tradition and to be of service and benefit to others. So that is what they do.
Of course you can do all of these things. What are you waiting for?