Where do I begin with my move to Rome?

Hi, I'm Lisa! I'm a writer currently living in California, and I'm beginning the process of planning a move to Rome . . . I would like to be there by early 2019. I won't need to look for a job in Italy as I do enough work for companies in the states to have a steady income (although I might like doing something part-time there in order to get out and meet people, learn/use Italian, etc.). Please help: Where do I start? I have a friend in Rome who will help me with basics like apartment hunting, etc. but in terms of obtaining a visa, what do I need, what do I do, etc? I visit Italy at least once a year and have decided it will be much better to just live there, at least for a year. I'm so in love with Rome, and this is the perfect time to make a move for me in my life. Help, please!