Once inside the SL Viewer I had to go to World at the top and select Parcel Details then you will see Abandon Land. Once I did that it let me Downgrade from SL website to Basic Membership. Hope this helps
Feel free to send me an IM as well🙂 Also I had my account for about 90 days but I tend to leave and come back due to the fact that I don't know much about SL and end up getting bored since I'm kinda lost on how to do many things on here .