If your domain DNS service is provided by GoDaddy,
1. You need to first delete the "A" records for both your root domain and www. To delete an "A" record, click the setting icon on the right side of the "A" record and then choose the "Delete record" option in your GoDaddy settings.
2. Go to Add or Edit a CNAME record of your own domain to point www to pbcdn2.podbean.com.
3. Add a TXT DNS record. Copy and paste the string Podbean generated for you in the "Content" area.
For detailed info, please contact GoDaddy for further help.