Well! How dare you call me socially awkward! :O What does your getting a job at McDonald's have to do with my being socially awkward, and moreover.....how do you know I'm socially awkward?! Well, I never! Huh!
Well, you have to practice talking to people. Talk, talk, talk. Practice interviewing with someone in your family who is good at getting hired, prepare answers for common questions at interview. Prepare and practice.
My recommendation is to let the job work for you. Use the job as a tool to improve your social skills. As long as you are polite, on time, and professionally presentable for the interview some fast food place will hire you even if it takes a few interviews at different places. I don't mean to imply you wouldn't get the job, but jobs are scarce. If you think a fast food job would be too much then start off in a position like a grocery store bagger because you are exposed to the public and you can work on your social skills.
Socially awkward , hmmm .. Never thought of my self as that . But if Iam and work at Micky D s . I would take advantage of the opportunity to practice my social skills , learn about people , talk , make new friends , I would also take advantage of all those French fries ... This is a learning experience , it's a good thing , no worries , you will do great !!
You don't unless your one of the people that just cooks or cleans stuff. Or just practice socializing with people and you will be more comfortable. Then you could be a cashier or the person that takes your order.