Aircraft you have purchased from the org store are downloaded from an E-mail they sent you right after your purchase. There is a download link in the email. This will be downloaded into your specified download folder. This is the only way to get a purchased aircraft from the org store.
Aircraft downloaded from the .org forum files are usually free and you download each one separately into your Download folder.
Do not unpack any zip from XP outside of your main XP folder. MS and security will fail and remove it. Move any zip inside the main XP folder and unpack it there. Then move the aircraft folder into your X-Plane Aircraft folder. Finished unless you have a verification to make the first time you open a payware plane in XP.