Harry Wilson made an appearance in the FA Cup, while Rhian Brewster was given the nod during a post-season friendly with Sydney FC shortly after the 2016-17 campaign came to an end.
"The boys did really well but they all have to improve," Klopp told the club's official website. "They have to go from being really skilled kids to being players that you have to use. That's the next step.
"Look at Rhian Brewster, everyone knows about his talent. It's fantastic. Ben is a step ahead and someone like Trent is already another step ahead. It's all cool and good for the future."
Liverpool have added another young player to their ranks this summer in the form of 19-year-old Dominic Solanke, who has agreed a move from Chelsea.