Go on the SC Secretary of State website and search for the name you want. If it's available it will say add new entity. The Entity has to have LLC at the end of the name. So you can call it Donut Operator LLC for instance.
The next screen you'll see a Form selection. Select "Yes Domestic Entity"
Choose a business type: Limited Liability Company
Select Articles of Organization
Click next and follow the next few screens. They are just asking your name and address.
Click Submit and pay $110. It normally takes a few hours for the secretary of state to review the submission. When it is approved you will get an email with the Articles of Organization. Make sure you keep these for your records. You are then ready to apply for an EIN for the LLC