I guess I should also add that when you get a bridge officer as a reward, you are given 3 options. You can either have the officer 'Join the crew', 'Train up', or 'not now'. Since you are just starting out, you should have him/her Join the crew. This will add the officer to your list of available officers which you can assign to a station on your ship, and be available to beam down with you on ground missions.
The 'Train' option is if you want to take one of the abilities that the officer has, and give it to an existing officer in your crew. If you pick this option, the new officer will disappear after training one of your old officers.
If you press 'u', and you bring up the list of bridge officers, you will notice that there will some slots that say 'No officer'. This means that this slot is available for an officer to join your crew. There is a max number that you can have, which increases as you level. These slots are what are referred to as bridge officer slots, and might be what you purchased.
FYI, you will be getting more bridge officers than you know what to do with as you level. If your available slots are full, you can pick the option 'not now', and the officer will go onto a waiting list. If you click the 'assignments' tab, you can see along the right side of the window all the officers that are waiting to join or train. Theses officers can also be sold on the exchange, or mailed to another character.
I just checked and I have a total capacity of 8 character slots.
I definitely bought 4 extra slots a while back.
So the default allocation I have is 4 slots:
2 at the start
1 from unlocking Klingon play at level 6
1 from the veteran reward.
I bought my lifetime sub as soon as I started playing exactly 400 days ago (I just got my 400 day accolade) and at that time and forever after lifetime subs DO NOT give you extra character slots. That offer ended immediately after the original launch of STO.
When they brought back lifetime subs sometime within the first couple of weeks of STO (the time I bought it), the lifetime sub DID NOT offer additional character slots and DID NOT offer liberated Borg playable captain. I was a bit peeved off, because the people who got lifetime before I was able to got extra slots and Borgs.
Sometime later, they suddenly turned playable Borg on for me and everyone else that had purchase the post-beta lifetime plan. But DID NOT give any extra character slots.
I still don't think that lifetime subs bought even today offer extra character slots. Go to http://www.startrekonline.com/lifetime and see that it does not say anywhere at all that character slots are part of the offer.