Stewart has joined Rangers on trial basis and will train with Alex McLeish's squad at their training camp in Austria.
"Coming home to Scotland was a massive factor in me taking this chance to win a deal with Rangers as I could have sat it out at Old Trafford for the next two years," Stewart told the Daily Record.
"The opportunity to be among family and friends in my home environment and the chance to play for Rangers flicks every switch and ticks every plus box for me. I'm at an age when I know I can improve. When I knew for definite I was going to leave Manchester United, my initial thoughts were, 'How big a fall will I have to take?' Then Rangers showed an interest.
"Rangers are a massive club and no different to Manchester United and I will bust a gut to make something materialise. I'm tired of talking a good game, I want to go out and play it. For two or three years, people have anticipated me doing something in football and I've had those thoughts. Rangers have handed me that platform and I intend to utilise it fully."