All FNIX Rising side missions must be activated from the warboard found in the Mullvadsberget Tunnels Safehouse (-1844.904, 1552.985).
Travel to -2801.835, 3554.919 and hack the gate open. Enter the compound and hack the supercomputer.
Now travel to -3830.619, 4141.430, hack the gate open and enter the compound to hack another supercomputer.
Travel one last time to -5458.535, 4424.954. Hack the gate (underground cave) enter to find a runner inside. Kill the runner to complete the mission.