You must live separate and apart, without cohabitation and with the intent to stay permanently apart, for 12 months after which you may file for a divorce based upon the 12 month separation. Once you (or he) file for the divorce, the other party must be served with the complaint and has 30 days to file an Answer (unless they waive the 30 day period).
There is no advantage to who asks the other for the divorce. In SC, you can both ask for the divorce and you can both have a divorce granted, one against the other, if you so choose.
My comments are not intended to establish an attorney-client relationship, are not confidential, and are not intended to constitute legal advice. Proper legal advice can only be given by an attorney who agrees to represent you, who reviews the facts of your specific case, who does not have a conflict of interest preventing the representation, and who is licensed to practice in the appropriate jurisdiction where the legal issue may be filed or in the state where the law applies.