Boga spent last season on loan at Spanish club Granada.
"It is different, I feel more mature in my game and I am better within the team," Boga told Chelsea's official website.
"I am more strong physically and I am better tactically as well, so I think I have grown a lot and I am very happy to be on pre-season with Chelsea.
"Even though last year was a difficult year for the team, I think I have learned a lot, especially because we had to defend and also technically I got better.
"Now in just the few weeks I have been on pre-season with Antonio Conte, I have been learning a lot tactically and he is good for me.
"He gives instructions for the strikers, for the way we play and the way we defend also. It is very tactical and I think it is what I am missing in my game. I am really focused because I need to learn more tactically."