I think what the OP meant was how many BO do you have right now? Meaning, if you press U, how many people show up after your ship. You can only have 4 at LTC, and you may already have all 4 slots filled.
I have two candidates. One Science that was a reward from a DO assignment and one Engineering that I picked up from the exchange. I don't think I even saw a commission option for either of them.
I received the Science BO candidate first and I do not have any open stations in Science. That's when I remembered that I had an open Eng station and looked for a BO to fill that slot.
My toon is a LtCmdr, 12, and my ship is a Constitution class. My first step up from the initial ship I was assigned.
Thanks for the feedback. I'm going to see about the commission option. I can recall using that for the first ones.
As you appear to understand, there are Bridge Officer Candidates (i.e., ones you own but have not put on your crew) slots and Commissioned Bridge Officers (i.e. those on your crew) slots. The piece it seems you are missing is that you can have a limited number of both of these types.
For BOff Candidates, I believe the limit is 12, and I know of no way to expand that, but I don't think there is a limit based on level, either. Since you only have two, that is obviously not the issue.
For Commissioned BOffs, you start out with a small number of slots, and you gain additional slots as you level at specific points. For Gold (paid) subscribers, I believe you get two additional slots at each point, and for Silver (free-to-play) subscribers, I believe you get one. You can also buy additional slots from the C-Store under Services (two slots for 250 Zen). I believe the maximum number of Commissioned BOff slots you can have is 54.
I believe the system is setup so that you will always have enough BOff slots to fully crew any ship you are eligible to fly without having to buy more, even if you are a Silver subscriber, but you won't necessarily have enough extra slots to have different crew layouts.
That sounds like the issue you are facing. You have not reached your maximum number of Candidates, but you have reached your maximum number of Commissioned BOffs. When you get a new Candidate, if there is an open spot on your Commisioned BOff roster, the Candidate will ask if you want him or her to join your crew (i.e., do you want to commission him or her) or train a BOff you have commissioned. If you are out of Commissioned BOff slots, he or she will only ask if you want to train an existing BOff. If you didn't get an option to add your newly acquired BOff to your crew when you got him or her, then it is a safe bet there was no room for you to do that.
When you are out of Commissioned BOff slots, you have to make room before you can commission another. That means that you either have to buy more slots or dismiss an already commissioned BOff.
As I said, I think (at least for Gold subscribers) you will always have enough slots to fully man any ship you are eligible to fly, but you just may not have enough slots to fly different types of ships with different BOff layouts or have enough to play around with different ability layouts (i.e., have more than one BOff for a given position). That being the case, it is likely that you have enough BOffs commissioned, but you have too many of one profession and not enough of another.
That means you will need to either dismiss one or buy new slots to make room for the new BOff you want to commission.