You have to promote the bridge officer to the rank in order to use each skill. If you are Commander then you can promote your bridge officer to the rank "Lt. Cmdr.", always 1 rank below you.
Now, you got an science ship for example. Science ships at Commander rank have 1 tactical station, 1 engineering station, 2 science stations.
At rank Commander, in your ship,
1 Science station is Lt.Cmdr
1 Science station is Ensign
1 Engineering station is Lt.
1 Tactical station is Lt.
So that means:
1 Science bridge officer will be able to use the first 3 skills
1 Science bridge officer will be able to use only his 1st skill
1 Engineering bridge officer will be able to use his first 2 skills
1 Tactical bridge officer will be able to use his first 2 skills
What skills your bridge officer can use is up to what kind of ship you are flying.
Ah so I need a higher tier ship! Crap! Well that means I spent my skill points wrong.