Star, you have to take your temp in the morning. First thing before you talk, get up to go the toilet, basically before you move. The whole point is to take your lowest temperature at the point of waking. You need to do it at exactly the same time each morning after at least 3 hours sleep. I just set my alarm for 6.30am. Wake up (hardly), stick the thermometer in my mouth, quickly look at the temp and if I can, roll over and go back to sleep.
Taking it at night will achieve nothing.
Please read up on temping. Taking Control Of Your Fertility is a really great book, but there's lots of info online. I'm happy to help if you have more questions.