You need to go to your registrar and change DNS settings for your domain. You create a new CNAME record for 'www' alias with 'wackwall.com' value.
This is basically what you need to do. If it's not obvious how to do it with your domain registrar you may want to ask for their assistance. For example, in GoDaddy you need to go to TotalDNS settings to create a new CNAME record.
If you already use your domain with a hosting account and want to use its subdomain for a social network from WackWall you need to add corresponding CNAME record on your hosting account accordingly. Check your hosting provider documentation.
After creating CNAME record for your domain you need to go to your social network administration area, basic settings: http://yourname.wackwall.com/admin-basics
There's 'Custom domain' field that will let you choose between working on subdomain (by default) or using your own domain name.
Warning: Improper domain name configuration will render your site unavailable after changing this setting. To return to the default (WackWall subdomain) mode you will need to go to your basic settings again: http://yourname.wackwall.com/admin-basics. This page is permanently available under WackWall subdomain.