Hi, My Girlfriend And I Wanted To Start Using Combined

Hi, my girlfriend and I wanted to start using Combined Oral Contraceptives as a method of birth control but we have no prior knowledge on it.
We've had these questions that we really wanted to get answers to befor we started using them:-
What should we consider before using it?
How does it work?
Will it be okay to have sex without condoms?
What are its effects?

Thank You,
-Mwatsama-