The Colombia international is joining Villa for around 18-million Pounds from Chicago Fire.
The club have also agreed to sell Danny Ings to West Ham for 15-million Pounds with Emery revamping his forward line.
He insisted Duran is not expected to replace Ings - with Villa also after another striker - and patience is required with the 19-year-old.
"He has potential as a striker if he can develop like we are thinking he will do," said Emery, ahead of Saturday's trip to Southampton.
"We can't give him the responsibility, as a 19-year-old, to play as a striker in the Premier League against the best teams in the world.
"I want to help him firstly with his adaptation; hopefully that will happen quickly. I know that he's coming as a 19-year-old and he will need time to know his team-mates, our ideas, and playing against important players in every session here and against opposition teams.
"We are going to help him. The responsibility now, as a number nine and a striker, is for (Ollie) Watkins. We want to add him (Duran) to help us.
"I want to balance the squad by trying to get another striker but only with the idea to improve us."
Saints are bottom of the Premier League on goal difference, below Everton and West Ham, and a point from safety.
Their 2-1 win at the Toffees last weekend was Saints boss Nathan Jones' first victory in the top flight and Emery remains wary.
"They are at the bottom of the table and they need points. They are signing players as well and they are going to do everything they can to beat us on Saturday," he said.
"They have very good players and now they are being more consistent than before. They have a better structure, defensively and offensively, to be stronger than they were.
"They are in the best moment they've played in the Premier League this season."