I know this isn't exactly answering your questions, but I'll say it anyway. Don't worry about beating certain times to begin with, just run the distances frequently. At least three times per week should suffice, if that is possible. Time yourself on each occasion and begin to notice the progression take shape after a few weeks. Your motivation can be to try to beat your previous time.
Your times will be erratic, especially at the beginning, but you should notice a general trend. I followed this method, for 3km, and I was knocking about 15 seconds off my time each week. However, as time passed by, I found it more and more difficult to shave seconds off my time. Once this has happened, I began to compare the time that I was consistently running, but not really beating, to what other keen runners were managing to achieve over the same distance.
The important thing, which I'm not successfully managing to succinctly articulate, is that it is a progression over a long time. I don't know what you are capable of right now, but I imagine it would be quite a long way off what you want to achieve in the long run?
If you could manage 7 minutes in the 1500m now, but are aiming for 6 minutes in the long run, do not go out in your first fun aiming to beat 6 minutes. That will only result in you losing time. Pace and energy management is really responsible for about 25% of your time in middle-distance running. Experienced runners always say nobody should ever set off to beat a time they've never achieved.