i got my HRM and found out that my heart rate on a 6mph run for 2.5 miles was 175-185. i was totally shocked because of the high heart rate for relatively low speed of my running. I am 23 yrs old and wonder what is are some good guidelines for increasing aerobic capicity and general health. Should i be running at 60-80% of max or maybe 50-70% i dont know, any advice is appreciated. Should I train differently on my bike that I do on the treadmill.

I handle that speed at around 150+ bpm, which is usually where I warm up at. My max HR is 206. Other than that, I think there are some possibilities:
1) You are out of shape
2) You could be overtraining - since you only used it recently

Do check out your resting heart rate. Do not train for a few days and see if your resting HR goes down day to day. If so, you are probably slightly stressed. Go do a workout after a few days of rest, a light one, and rest another few days. Over time, if your HR does not decrease much. It is more likely that you are not overtrained. If so, train based on the HR + perceived effort. If it is okay, train at any percentage depending on what you are doing that day. It never hurts to train at times harder than what your HR is telling you. HR is rather inconsistent and not really reliable compared to power output vs HR. Since you are running, experiment and see what fits and what doesn't. You need to know your body.

Don't worry too much. The human body is slothful and it is very easy to get way out of shape. Also when you first start doing aerobic exercise almost anything can push you to near anaerobic. This is really easy to do running by the way because unless you are very thin and very fit, anytime you run at more than a jog, you will get stressed.

When I started cycling years ago, (before heart monitors), I just went out and rode. I rode a bit farther as time progressed. First it was round the neighborhood. Then it was into adjacent neighborhoods. Then it was into the country a little. Then it was to the nearest little towns. Pretty soon, I was doing centuries. I made mistakes like my first 30 mile ride which I did without water and I got nailed by heat exhaustion. If you stick with it and are patient, you should do fine.

my running HR is ALWAYS higher than my cycling heart rate. Running is a great (in fact i think it is the best) way to increase aerobic capcity.