Click on the paper clip-icon above the text field.
Depending on the location of the file you want to add, click Add Attachment from Hard Drive or Add Attachment from Cloud.
Select the file you would like to attach.
You may select multiple files by holding the
Ctrl key and simultaneously
clicking on a file name.
Click Attach or Open.
If necessary, you can attach additional files by clicking the paperclip icon
Afterwards, send the email as usual.
Attaching large files via sharelink
Large attachments can be sent by email using a Cloud share
If you're trying to send an attachment which exceeds the size
limit, you can upload the file to your Cloud and have the
recipient download it via the share link.