You need to do this yourself on the manage domains page in the panel. If your domain is already listed there edit it to make it DNS only. If it's not listed there yet use the button at the top of the page to add it, again DNS only.
After it's listed there, click the DNS link below the domain name and add an A record with the value being that IP address.
Next step is wait. DNS changes don't happen very quickly, usually 4-8 hours but maybe even a little longer. Since there appears to be no A record at all for that domain right now, it may happen much faster in this case. Just be patient and don't keep changing things because you're not seeing the weebly site come up right away under your domain name.