Need help with the 1500m and 400m race?

So this week my track coach begged me to do the decathlon for high school track (I'm a junior) and two of the events are the 1500m and 400m races. The meet is this friday. I am a thrower (javelin/shot put/discus) and have never ran a race in a meet before. Obviously I've ran before but never timed or anything. So my question is how do I run these two races, like what pace should I go at and are there any tips or tricks to these races? I'm a decent runner, I think my sophomore year I did around a 6:20 mile. But anyway any help would be appreciated!! Thanks!