My idea of taking meds at night is remembering to take them any time between 8pm and midnight! (but I'm not a role model for taking meds...)
It is easiest to remember if you do it at the same time as something you regularly do like brushing your teeth...
I am sure that the doctors had a reason they wanted you to take this med. I am also sure there was a reason why you went to the doctors. Try to remember this when you don't want to take your meds. (I hate taking mine some days...)
Also try to get your doctor to explain what he is giving you, what effect it should have and when, and any side effects to look out for. The is a lot of information available on bipolar and types of medication available online if you think that would help you.