First of all, you would need to contact SNAFU by sending him a message from his store page on the Shapeways site. He will send you his files in his reply, then you download them to your computer. Once you have the files on your computer, go to your Shapeways profile and click on the MY WORKSHOP tab at the top of the page. There will see UP LOAD A NEW MODEL, click that and browse for the file you want. If I remember correctly, you will need to un-zip the file once you download it to your computer. I has been awhile since I have done it. I am sure someone else here is far more savvy than in that department than I. Hope this helps.
I picked up some orphan aircraft and I am searching for the matching cards. I am looking for (3) SWORDFISH MK1 and (1) B6N2 JILL. I have cards for trade or I am willing to pay cash.
Get on the SHAPEWAYS site and go to the SNAFU store by Echoco. If you contact him, he will generously give the file to you to put in your SHAPEWAYS workshop.