So it's Tuesday in the first week. You've run your first run by now, how'd it go? If you had a hard time with the run, you may want to incorporate walking breaks (idea first mainstreamed by Jeff Galloway) into your runs. You might want to try these if you had trouble just staying under the 70% HRM.
To try these, there are a number of ways but I'll simplify it by asking you to run 5 minutes at > 70% and then walk 30 seconds, run to the 10 minute mark, walk 30 seconds and just repeat until your 4 miles are done. These walking breaks help your body adjust to the new stress. These walking breaks can be incorporate the same way for your long runs if you find them difficult also.
Tomorrow you are slated for a Tempo workout. For Week One, move into these carefully by warming up for one mile at >70%, run a mile in the 80-88% range, .25 mile walk or easy running, mile at 80-88%, .25 mile walk/easy run, 80-88% mile, finish with a half mile walk easy run.
Remember, you need to stay in these zones in the training. You may find that you last Tempo mile is at a slower pace than your first Tempo mile. That's okay, what's important is that you stay in that zone 80-88% during the mile. We're looking at heart rate zone, not timed speed for this exercise.
I will have another update for you Friday before the Long Run, so that you get started with a good first long run.