This is the correct program, and is part of Dual Enrollment, which has 3 programs.
To register, first you need to find the person at your HS who coordinates this. Your counselor will know who that is. Then they will connect you to the MC coordinator, and you’ll work with both of them to get registered. It’s a tedious process with a lot of steps but worth it in the end.
Note there’s a list of courses that MCPS will accept for credit and pay for. You can still take courses that aren’t on the list but will have to pay and you won’t get credit. Also, they won’t pay for summer courses whether they accept the credit or not. Classes are about $500. When they take credit, it will show up on your MCPS transcript and count in the five point scale for your GPA.
You’ll have to take placement tests. For English you write an essay and for math you use a service called Aleks.
It’s kind of a nightmare administrative task, so you might want to ask a parent for help, or it could be a good learning opportunity.
Good luck!