Always Remember: Going to College is a Full-time Job. You should be studying 2 hours for each credit hour that you are taking. If you are taking 15 credit hours, that means that you need to be studying 30 (15x2) hours per week for your classes. That's a total of 45 hours a week that must be dedicated to School! That's a Full-time job!
Using a paper-based planner is a great way begin. A lot of us use the Calendars on our smartphones, but it's a good idea to begin with a planner when starting out.
This can be a tough pill to swallow, but sometimes we need to eliminate the time wasters in our lives. This can be a video game system, Netflix, Social Media, and sometimes...your friends.