Defoe has replaced Neil Ardley at National League Woking in first job as manager.
"It's been a long time coming," 43-year-old Defoe told BBC Radio Surrey.
"It was always the plan at the back end of my career when I knew I wanted to go into coaching and luckily enough that transition was quite smooth.
"I left Rangers, I went straight into Tottenham and did two years in the academy. I was exposed at Rangers a little bit with a player-coach role in my last year.
"When you look at the infrastructure, it's somewhere where I hope players will want to come and play. The talks have gone on for a while and I just want to get going."
Woking sit 10th on the National League table, 11 points off the play-offs with six matches of the regular season remaining.
"I don't want to sit here and say, right, we need to achieve this, we need to achieve that," Defoe added.
"We're ambitious people, I want to do well.
"The main objective is, of course, to get promoted with the players we've got, some top players. The games that I've watched, I've been really impressed.
"You have to be confident. I think you always have to back yourself, whether you're a player or a manager or a coach."