The 56-year-old replaced Allan Freese as the club's coach on Tuesday, having been without a job since his sacking from SuperSport United in August.
Johnson - who has retained Willem Jackson as his assistant - previously guided Stars to a second-placed finish in the League in 2012/13 behind Kaizer Chiefs before switching to United last season.
He told Dikwena's website: "When one leaves a company, it is good not to burn your bridges. My departure was not bitter, hence I was approached at this time. I am not a magician but Platinum Stars believes that I can change the game, and I will definitely try with all that I have to succeed this team. We once built good memories, we must take it off where we left off. I see a lot of good memories."
Johnson's first assignment will be against Ajax Cape Town at Royal Bafokeng Stadium on Saturday night.
"It is a very important game that one and we need six points from that one. You must understand that our situation is not an appealing one but with the team I have, come and just observe, we will enjoy every moment of victory," he said.