It appears that you were flying under part 135. Some questions:
Did you receive a part 135 SIC checkride?
Was an SIC required by your OPSPECS?
Were you flying passengers and was there an operable autopilot?
Were there any Part 91 legs?
Were you the sole manipulator of the controls?
The answers to these questions will help us understand your situation a little better. Depending on the situation, you could legally log PIC, SIC, or nothing. What to put on AirlineApps is another matter that can be more readily discussed with this information.