The Senegal international was preparing for Newcastle’s clash against Everton last week when he was made aware of the London club’s offer for him.
Ba has admitted he was eager to join Chelsea because of the club’s size and its squad of "world-class players".
“When you know a club like Chelsea wants you the decision is going to be easy,” he told TalkSport. “With all due respect to Newcastle, because Newcastle is a big club with a big history.
“I woke up on Wednesday and prepared myself to play against Everton, I got a text from the manager to tell me I need to come and see him and from that moment I knew that everything was fixed for me to go.”
Ba made 54 first-team appearances for Newcastle since joining them from West Ham in 2011, scoring 29 times.
“I’m very happy, very pleased to play with these players [at Chelsea].” Ba continued. “They’re world-class players and when you play with them it’s something different, they’re really intelligent in the game.
“I just want to enjoy my football here and that’s what I do.”