How do I develop a plan for running on the treadmill as a beginner? What settings do I choose?

I am just starting to run again and I have no idea
a. how long i should be running
b. what distance i should be running
c. how many times i should be doing a workout routine
d. what settings to put on the treadmill (what time intervals to alternate walking and running, too)
e. what my heart rate goal should be? (or other goals)

I am a 19 year old female. I am 5'8 and I weigh 115 lbs. (i also used to be a dancer for 9 years if thats relevant) I am very out of shape though even though I'm skinny. I guess I am trying to drop a few pounds but really I just want to become a good runner so i can be healthy and be in good shape :)

I usually just alternate between walking and running (walk for 10, run for 5, walk for 5, run for 7, walk for 3) and when I run I put the speed at 6 (sometimes at 7 or 8 for a 2-minute sprint), and when I walk I put the speed around 4. I just started this routine a few days ago and so far its exhausting and will give me cramps (which i can deal with in the beginning of getting back on track)

Anyways I really need some kind of personalized plan (maybe one that will help me ease into working out too because I have been pushing myself too hard these past few days) but I can't afford a personal trainer and my gym doesn't even offer that because i go to my university's gym.

A rough-estimate plan/schedule would be helpful, or a link to a website that develops personal work out plans would be really helpful, or maybe even an article. Anything helps! Thanks C: