The experienced stopper is the latest arrival at Ibrox.
The former Norwich City and Blackpool stopper joined the Gers on Friday on a free transfer after his contract with last club Burnley expired and Stewart is pleased to have him on board.
“(He has) plenty of ability, a good type about the dressing room, good character, played at the highest level in terms of playing in the English Premiership and obviously he’s been in about the Scotland squads,” said Stewart.
“I know him from that as well and he’ll bring good experience and good knowledge and good enthusiasm and a bit of humour to the dressing room.
Gilks did not see much first-team action at Burnley and will face an equally tough time at Ibrox, with Wes Foderingham coming off the back of a hugely successful debut season.
The 34-year-old will bring experience however, and will give Foderingham slightly more to think about in terms of the security of his number one spot in the coming months.
Gilks' signing made it six so far for Rangers this summer as Mark Warburton continues to assemble a squad capable of competing for the SPL at the first time of asking.
The likes of Joey Barton and Nico Kranjcar have added real quality to an already strong Gers team and Celtic will be well aware that making it six in a row next season will not be a mere formality.