You have all the powers that Putin currently does. Everyone feels the same way they do about you that they used to about Putin. You have his authority, for as long as you can hang on to it. You have none of his knowledge, however. The economic, military, social and political situations are the same as they now are. You are not inhabiting Putin’s body, you are just you. You’re magically transferred to the Kremlin.
How do you avoid falling out a window onto a pile of bullets your first week?
Arrest and kill all the oligarchs that were previous Putin Loyalists, replace them with technocrats in a transitional state, institute a federated democratic system.
Anyone who’d want me dead is gone, anyone with power is loyal to me or apathetic on the issue, and the people now see me as a national hero, especially in the resource rich regions mainly inhabited by ethnic minorities who will now likely raise riot if anyone tries to take them back to the old ways.
Also try the patriarch of Novgorod for treason if he tries to pull anything.