Apply for admission into a postbaccalaureate degree program by fulfilling all the requirements of your desired school. Rely upon your academic advisor to guide you through the application process.
Ask some of your previous academic professors to write letters of recommendation, as well as a letter providing an explanation for your low GPA.
Mention extenuating circumstances. For example, if your GPA isn't higher because you all at once are full-time student, hold a full-time job, are a parent of three young kids and take care of a sick parent, let your prospective school know. Do not make up excuses for your low GPA, but be honest.