Others are being nice, so I want to be blunt and honest you failed this one simply because you did not read and follow the instructions given to you by the agent in the mission briefing.
Advanced Military Career Agent
So where to go from here.
First I suggest reading your mission briefings more carefully so you understand what you are required to do.
You can simply wait until the next downtime, most missions that have not been completed will reset at downtime.
As mentioned above you can petition the GM to reset your mission, or you can simply abandon it and the rest in the string and go elsewhere. I suggest you ask for it to be reset before anything else. No having this mission open will not prevent you from running other missions as long as they are given to you by a different agent.
When you get back to this one and all missions please read and understand what you are supposed to do. Especially the career agent missions require you to complete a specific task, and any deviation from what you are told to do will result in failing the mission.