When you are viewing your model in the public viewer, you can click the "Inventory" tab, then download the BrickLink XML file. Then you can upload this file to BrickLink and have it create a Wanted list with the parts. From there, you can use the normal BrickLink process to buy the parts.

I'm trying to upload the XML file content directly since Bricklink won't accept the file formatting, I'm copy and pasting its contents into the "upload Bricklink XML file List" but its saying "Invalid File Format: Content is not allowed in prolog.". Please help me...

I'm going to assume that there was some kind of normal text in front of the XML file. An XML file in this case should start with <INVENTORY>.