Stones joined City from Everton in a £47.5million deal this week after a pursuit that had lasted most of the summer.
With captain Vincent Kompany injured and fitness doubts over Nicolas Otamendi and Eliaquim Mangala, Stones is likely to find himself straight in the side as City host Sunderland on Saturday.
Guardiola said: "Finally we could pick John up
I think it is important for us - an English player, a young player, a huge talent, not just with defending but with his intelligence to read the next step, the next pass, behind the line.
"I think he is a good, good, good player, so we are happy to have him and he is fit
He played with Ronald Koeman (at Everton) four, five or six friendly games, of 90 minutes, so he is fit."
Guardiola has overseen eight signings since taking charge earlier in the summer and admits he does not yet know what his best team is
The former Barcelona and Bayern Munich boss also says it will take time for his methods to take hold, although he will demand the highest attitude from the start.
The Spaniard said: "I know maybe 80 or 90 per cent who will play tomorrow
Maybe I need my dream tonight to make the right decision.
"To create something we need time, to create something with ideas to attack we need time
But to play with soul and something inside we don't need time.
"Tomorrow we don't know if everyone is going to play good or if we will get the result but I will not accept not playing with soul
We can do that from the first day and that is exactly what I am looking for from my team and my players.
"To create something, obviously we have to play games and it is so important to win for our confidence."
Three of City's summer recruits in Gabriel Jesus, Marlos Moreno and Aaron Mooy are not in immediate first-team contention while Leroy Sane and Ilkay Gundogan are injured
Midfielder Oleksandr Zinchenko and striker Nolito could be handed debuts alongside Stones.
Guardiola insists he is happy with England number one Joe Hart as his first-choice goalkeeper as things stand.
Hart's future has been brought into question by reports suggesting Guardiola may consider bringing in a new keeper.
Speaking at his pre-match press conference, Guardiola said: "Today is not about Joe
Today is the day before the start of the Premier League.
"Joe is a player I'm so happy about (with) his qualities, his behaviour, and what he means to this club
After we are going to decide inside the doors
Now, he is a player of us."
City have spent around £153million on players this summer and Guardiola has not ruled out further additions.
He said: "August 31 is the last day
We are going to see which players will stay, which players are going to be loaned, which are going to be sold, which players coming."
Source : PA
Source: PA