There are two ways to send files in emails -- either via attachment or by including a link to the file in the email. We don't currently support attachments on emails because we've seen issues with deliverability with attachments -- emails going to spam folders more often, etc.
Instead, we've got the ability to upload files to your account so you can include links in the email. Here's how you do that:
First, go to the files section in your account and upload a file:
Once the file is uploaded, go into Actions and copy the link:
Then, in the email template, use the link or chains button to create a link to the file:
Put the link in the Url box and the text you want to show on the page in the "Text to display" box.