I have a little bit of experience with AAS and endurance training. Might have run a marathon or two while on cycle. It would be most helpful, however, if you can put up some stats in your profile. Maybe an avatar. A little introduction about who you are so I can best help you.
You will find that your first cycle should be the same regardless of why you are using it. Test and test only. 500mg a week in two pins is the norm. If you want to succeed you will need to have your diet planned out. If you are training endurance then you'll be hitting the carbs more than normal. You will need to balance this, as well as increase calories. Yes, even if you are planning on trying to lose fat, you need the calories while running + building muscle. It isn't an easy chore. Think of eating as another workout. that is how i do it. force that extra cup of cottage cheese down like that last set.
After we get to know a little more about you we can offer more advice.