If you haven't incorporated, then you're a sole proprietor. Centurion is right on the schedule C. But you also need to pay estimated taxes quarterly if you are above a threshold. Part of it depends on whether you are also paying taxes as an employee. You also need to register with your state and county and pay any local taxes they have.
None of it is overly complicated after you do it the first time, but it can be confusing the first time, so if you're confused, go for the accountant. There can be fees and penalties for not filing or filing late, so don't ignore this or put it off until the end of the year.