ok, once I've recruited a new officer to my team how do I assign him?
You'll get a dialogue box with "Join" "Train Up" & "Not now" as optional replies when you requisition a new BOff. If you want him/her as part of your crew, pick "Join". If you accidentally dismiss this dialogue without doing anything, you can find him/her again by going to your "Stations" tab, (s)he'll be listed on the right hand side. Double click on them to bring up the dialogue box again. Once he/she's in your crew you can then assign him/her to a station by pressing U and going to your "Stations" tab.
You'll probably need to bring him to the Officer Trainer first to have his abilities matched to the one you accidentally dismissed.
("Train Up", btw, will have the BOff train an existing BOff you have in one of their skills. This then uses up that BOff)