Ship-to party ##### is not defined for sales area

Hi all! I'm in the process of creating a sales order and I keep getting the above error message "Ship-to party ##### is not defined for sales area'. Can someone please tell me how to fix this? I saw other posts asking this but I didn't understand the answers at all because I don't know what "VD02" and other terminology is. Also those answers are based on very old versions of SAP while I’m using the newest version. Can someone please explain how to fix these problems in easy terms? PLEASE HELP!!!