The German takes charge of his first United game on Sunday when Crystal Palace visit Old Trafford.
The 63-year-old will be tasked with turning things around following the sacking of OIe Gunnar Solskjaer, with a top four finish a must.
The Red Devils are 14 points off league leaders Man City and Rangnick dismissed the club's progress so far this season as 'average'.
Writing in the Manchester United programme, Rangnick said: "Good afternoon. Managing Manchester United, even in an interim capacity, is a massive challenge but, to me, this feels like I am in the right place at the right time.
"I have been here at Old Trafford before, as an opposition manager with Schalke in the 2011 Champions League semi-finals, while also watching matches from the stands on other occasions. I also visited Manchester a couple of times while my eldest son spent three months studying at university here, and I am delighted to be back again.
"Manchester United is one of the biggest clubs in the world. There is so much history here, so many titles won, so many great players produced and developed.
"Right now, I am here because development is what needs to happen again. Nobody at the club is happy to be where we are in the Premier League table. It has been an average season so far, there is no avoiding that, but the club has players who are much better than the position we currently occupy and it is my job to improve those players and that position.
"There are some vastly experienced players in the squad, as well as so many talented young players. I look at guys like Jadon Sancho, who I know from the Bundesliga, Mason Greenwood and Marcus Rashford, and I am very much looking forward to working with the entire squad and helping them all to make the most of their obvious talent.
"The first step in doing that is a shift in how the collective approaches games. If you want to win a football match, you have to control it, so the aim right now is to help the team control games more. That means being more proactive with and without the ball.
"It is important, first and foremost, to start winning games regularly in the short-term then step by step, build the team in the right direction beyond that. We want to train the players' brains and encourage them to do the right things until they become second nature.
"It is difficult to look too far ahead, of course. I am here as interim manager until the end of the season, but in the very short-term my priority has to be to get to know the players. Obviously, that isn't easy right away because I have arrived at maybe the busiest time of the season and there are very few gaps in the calendar!
"In the end, we all want Manchester United to be performing successfully and playing in style. We all have a lot of work to do in order to get there and I'm very excited about the process, but today we welcome Crystal Palace, managed by Patrick Vieira, and finding a way to win this first game is my only focus.
"It is a challenge, especially with so little preparation time, but it is a challenge that I am relishing."