Was hired as a temporary employee (not through an agency) for one year and was told by HR that maybe after 6 months they would consider bringing me on FT. Would it be better to express my interest with HR instead of my manager since they were the ones who originally mentioned it?
You’ve got your answer but I want to add: You manager, or their superior, is who informs HR that you are now FT. HR doesn’t move people around in any way except sometimes to terminate an employee, and even then they don’t initiate that call, management does.