You need to "unlock" the ability to speak to Four of Ten, Captain of the U.S.S. Victory.
To be able to contact her, you need to do the 1st mission ("Report to Gamma Orionis") of the Borg Collective Episode.
Assuming you have not changed the default hotkeys, "j" opens the User Interface you want. Go to the "Episodes" tab across the top, and check for the "Borg Collective" tab down the left side.
I will guess that the Borg Collective tab is greyed out for you. From here you have two options:
1) Play all of the missions until you unlock the Borg Collective Episode
2) Skip as many missions as you can until you unlock the Borg Collective Episode. Note on this point: you can't skip every mission. At the very least you need to meet the minimum level requirements of the mission you are trying to skip--Level 42 required to skip the last mission of the "Cardassian Struggle" Episode. (Since you need to be Level 44 to run the Special Task Force missions, this should not be a problem for you.) You are also required (as far as I can tell) to complete the first mission of each Episode, aka cannot be skipped.
Once you can speak to Four of Ten, the Borg Science Bridge Officer Candidate award given by the "Assimilated" accolade from the "Khitomer Accord" Special Task Force mission should be offered to you.