Whilst you do not need any technical skills to point your domain name to your google site you MUST be very careful and patient or you will go in circles, wate time and get frustrated so please follow these instructions.
Now enter your domain and then click "Verify your ownership" see below;
Add a new CNAME record for www pointing to ghs.googlehosted.com see below;
Now delete any existing A records add A records
216.239.32.21
216.239.34.21
216.239.36.21
216.239.38.21
as follows;
Now try out some advanced Google site features while you wait 2-24 hours before checking if your new custom domain name is active.