How to manage working two jobs and taking college courses?

Hi all, I’ve recently picked up a second job at the mall, and I am wondering how I will balance my first job working at a hotel and working my new second job as well when school starts again?
Currently, I am on summer break and will be off for several weeks.
I find this as a good time to pick up a second job and make a little more money on the side.
My first job I have a set schedule and work five days a week for about 8 hours a day.
My new second job I believe I will be working 20 hours a week, so possibly 4 days out of the week for 5 hours at a time.
But my question is, how should I go about managing my time when school comes around?
I only plan to take one class at a time, but it’s really hard for me to sleep at night.
I figure maybe having a calendar would help me in the long run…

Thanks.