If you have large files which acts as inputs to your custom job that you need to send to us, follow these steps
Go to https://wetransfer.com
Click on upload files, select the file you want to send.
Once your file has been uploaded click on the 3 circles.
Choose to send as a 'Link' and then click 'Transfer'
Once complete click 'copy link'.
You can enter this link in the We transfer file upload links field while creating your data extraction job