What I'm wondering is, can we make this any clearer to reading users. Obviously, we can't put in a complete explanation of how DNS works, but I think we probably could expand on what we currently have ("LiveJournal does not provide DNS services. You will need to obtain DNS services from your web hosting company or your domain registrar."). I'm thinking something along the lines of the following:
Setting up your domain's DNS typically contains two parts. First, you must specify two DNS servers (an "NS record") and then you must specify what IP address these point at (an "A record"). Different domain registrars will provide you with different levels of control over these options. Typically, you will not need to change the NS record at all, but need to change the A record as explained above. LiveJournal does not offer a DNS service, so it is not possible to use this feature if your domain registrar only allows you to control your NS records, or does not allow you access to DNS records at all. If you are unsure of how to make the required changes or do not know if your registrar offers you the ability, you will need to contact them, explaining that you wish to have your domain's A record point to 126.96.36.199.
I'm not particularly happy with that wording, so any improvements would be welcome. I'd also really like if this could be checked over by people more familiar with DNS than I am to check that it's technically accurate, and by people less familiar than I am to check that it's comprehensible.