WeTransfer (easiest, no account needed):
Visit wetransfer.com → drop your file in → choose "Get a link" → copy the link → paste it on the form.
Google Drive:
Upload the file to your Drive → right-click it → Share → change "Restricted" to "Anyone with the link" → click Copy link → paste it on the form.
Or, in the Share window, type hello@them3dprintguys.com and click Send, then still copy the link and paste it on the form so we can match the file to your request.
Dropbox:
Upload the file → hover over it → click Share → set to "Anyone with the link can view" → Copy link → paste it on the form.
File under 25 MB? You can also email it as an attachment to hello@them3dprintguys.com, but please still submit this form so we have your request details.