The change itself could only be approved by the Pope. The first change allows the dates of the Conclave to be moved up, before the 15th of March, if all cardinal electors are in Rome.
MONS. PIER LUIGI CELATA
"The Motu Proprio still notes this window of 15 days, but it gives the College of Cardinals, the power to move the date of the Conclave before this window. That is, if all cardinal electors are in Rome."
Before this modification, the Conclave could only begin 15 days after the death or resignation of a Pope.
Once the Pope resigns, cardinals will begin to meet on a daily basis, starting on March 1st. It's a time to discuss the state of the Church, its strengths and challenges.
FR. FEDERICO LOMBARDI
"First cardinals need to have their General Congregation meeting, and they will probably not decide the date of the Conclave in their first meeting on March 1st. I think they will wait a few days, before making a formal decision.”
Other modifications to the constitution, have to do with the seal of secrecy and the sanctions for those who break it. It's not only cardinals who have to maintain a vow of secrecy during the Conclave, but also those who are indirectly involved in the Conclave, like security or health technicians. Not doing so could result in ex-communication.
Through a message the Holy See's Secretary of State Cardinal, Tarcisio Bertone called on all those who lead a consecrated life to pray for the Church during this special time.