Yeah that happens as you get older, particularly if you haven't done much exercise in between. 8-9 minutes per mile isn't terrible to start from, could be worse.
The /roon/ thread has a list of resources to draw from for guidance but if you have done cross and track before you will be familiar with the basics: start with low mileage, build slowly, add some slightly quicker efforts as you get stronger but mostly be consistent and try to avoid overdoing it (illness & injury).
Don't worry about mileage to begin with, concentrate on duration.
One thing many anons do is push mileage too hard without paying attention to speed. 18 isn't particularly rapid but its not hanging around either, so you will need to keep half an eye on developing the mechanics for running at more than a shuffle. Include some strides at the end of an easy run once or twice a week from early on (not a sprint though).
Be patient, it takes time to get back.

>>76732096
i think agility ladder, step drills, and drills where you turn your legs over at a high rate get you comfy running hard over mile-5k distance. running times contain a huge weight penalty too. i try not to let 48 hours pass without a workout

read running with the buffalos for a sense of the internal life of fast runners in college and train with their spirit and pride etc

>>76732343
forgot to post this, kicking my ass with my heel was a good cue to flex my knee more on the back leg turnover and stop slacking

>>76732343
Weight - yes, didnt mention it straight off as there's pervading dismorphia on /fit/ and athletes (particularly women) will obsess and fuck themselves up over it.

That said, there are tables available that allow you to calculate pace at VO2max vs weight. Lose weight, run faster is the overly simplistic message.

>>76732096
If you can't run faster than an 8 minute mile, then you need to be running more 10 minute miles.