The former Kilmarnock striker has moved to Ibrox on a free transfer, with Ally McCoist confirming an offer has been lodged for Craig Beattie ahead of September's transfer embargo
The 27-year-old joins Ian Black as Ally McCoist's second signing of the summer following the Scottish Football Association's decision to relegate the club to the Third Division and impose a transfer ban, which will begin on September 1.
The Northern Irishman, who left Kilmarnock at the end of last season after helping them to victory in the Scottish League Cup final, has described the move as a "personal challenge."
"There were moves to England and abroad but none were the size of club that Rangers are," Shiels said, according to Sky Sports.
"There has been interest for a while now. Knowing I was wanted, a few months ago, when they were still in the SPL, was a good factor.
"I felt wanted and I was keen to come here. As soon as I spoke to the manager, my mind was made up."
When it was suggested that moving to the Scottish fourth tier was a step down, Shiels replied: "I don't care.
"There are going to be critics and people will give their opinions but I've made a decision for myself and for my family and I'm delighted to be here.
"I see it as a challenge, as a personal challenge, to try to do my bit to get this club back to where it belongs, back to top-flight football.
"First and foremost, I wanted to sign for Rangers. No matter what league they are in, it's a massive club."
McCoist, meanwhile, is aiming to secure further acquisitions ahead of the 2012-13 season before the embargo sets in.
"I have meetings with [chief scout] Neil Murray and [chief executive] Charles Green tomorrow," he told the club's official website.
"We will push a few names forward and see where we go. Charles has spoken to Craig Beattie's agent and he made him an offer.
"As yet, I have not heard back from him or from Craig but hopefully I will do in the next 24 hours."
McCoist also reiterated his desire to see Carlos Bocanegra and Dorin Goian remain with the club and not follow the raft of senior players to leave Ibrox over the last month.
"As far as I know, both Carlos and Dorin are staying," he revealed. "We don't want to lose the spine of the team and those two centre-backs make up a great part of our team so hopefully they will remain with us."