For the (In)Security mission in Dubai, you will need to disguise yourself as the recruit to get access to the target, Marcus Stuyvesant. This will take a little bit of work, and you will need to start by getting a completely different uniform. If you look up in the main Atrium you will see a balcony on the right with a lone security guard up there. Work your way up to him and take him out, and put on his uniform.
This acts as something of a shortcut, as you already have the uniform that you need. From there, follow the waypoint to find the recruit, who is down in the staff area in a changing room. He is waiting on his uniform, and you can easily grab his papers while he is complaining.
Another option is to head back to the meeting room where you met Ingram if you still have the outfit the other assassin was wearing. You can go into the meeting room then out the other side and find some Penthouse guards that are easy to take down. This uniform will allow you into any staff area, making it easy to get to the recruit.
If you don’t already have the uniform, you will need to disguise yourself as a security guard. Follow the waypoint again and you will reach two guards wearing the correct type. One of them has a waypoint on him, but you can ignore him. You don’t need his uniform, just a uniform. The guy with the waypoint will wander up and down the hall, giving you the chance to grab the wrench from the cart beside the other guard, smack him in the head with it, and then drag him to the nearby bathroom. Grab his uniform and then carefully leave the bathroom, ensuring nobody sees the body.
From there, make your way to the security room to continue the rest of the (In)Security mission.