When you're ready to take the test, the Council says:
"The cost of taking the tests can vary by state, province, or program (collectively known as "jurisdictions"). Some jurisdictions offer the tests for free, while most charge a nominal fee to cover expenses of operating the testing center. Find out how much the tests cost by contacting your local GED testing center."
The Council also notes: "The GED Tests cannot be taken online. The GED Tests can only be taken at an official testing center," so beware of any websites that claim to offer the GED online.
Your local college should have a GED program. Go and talk to a counselor there. They should be able to walk you through the steps. Then once you get your GED, then you apply at the admissions office to attend there. You will need to see the financial aid office for grants and loans. They should be able to walk you through this too. Good luck! Once of my best college professors had a GED!