Can someone help me navigate the US copyright office.

So long and short I have made about 10-15 songs I actually like using BandLab. I was smart enough not to publish anything yet. However I have no clue what any of the copyright types are. I was told about Master Recording and Songwriting (what is the difference?) Should I do a multiple register, a single register. I just need some help trying to figure it out because youtube is not cutting it.