Do I need to face the 2 FM antenna bay of our radio station in only one direction? Also, do I need to face them to the sea direction? If yes why? Please enlighten me.
If it is a multbay dipole antenna, they are usually designed to allow some control over the radiation pattern. For example, this one can be omni or cardioid (it is not on the FM broadcast band, but the idea is the same).
As fa as "face them to the sea direction", that depends on where you want coverage. In any case, you will have to set them, and then use a field strength meter to check the pattern and ensure you got it the way you need.
To face them in the same direction, they must be "phased" together so their radiation pattern is in the same phase. An improper phasing may cause one antenna to cancel out the other (to a certain point).