PARIS — Against the regal backdrop of a grand reception room in France’s presidential palace, Emmanuel Macron, 39, was officially installed on Sunday as the youngest president in modern French history.

In his short speech to mark the occasion, he encouraged the French to embrace the future, to hold him to a high standard and to join him in the hard work ahead.

“I reassure you that not for a single second did I think that everything changed as if by magic on May 7,” Mr. Macron said of the day he was elected. “This will be slow work, demanding, but indispensable. It will be up to me to convince the French that our country, which seems threatened by the sometimes contrary winds of the world, carries in its heart all the resources to be a nation of the first rank.”

The new president is wasting no time. On Sunday afternoon, Mr. Macron, as the new commander in chief, visited wounded soldiers at a military hospital outside Paris. On Monday, he is expected to travel to Berlin to meet with Chancellor Angela Merkel of Germany, France’s most important ally in Europe, and will also announce his pick for prime minister. By midweek, the rest of his government is expected to be named.