Hey Malcolm,
Welcome to the Club! Getting started here is easy. You can post your wants or trade lists, what you're looking to sell, or just general questions. The grading thing can be complicated and probably has a lot to do with what you have and whether you are looking for a quick sale or holding them long term, at least that's how I look at it. Feel free to shoot me a direct message if you have any specific questions I can help with, especially regarding how the site works, but our member base are long time collectors and collectively have way more knowledge than me
Happy trading! -Andy