1. Click on the Blue Plus icon on the attachment field
2. A pop up window will appear. Drag and drop the file in this window, or paste the file in it. If you want to upload the file that is already on your computer choose My Device or browse files. If you want to take a picture right now and upload it, choose Camera
3. When you choose My Device a dialog box will appear. Choose your file(s)
4. Click Open
5. Click 'Upload (3) file(s)'
6. When the files are uploaded they are stacked next to each other
In case you want to see how drag and drop is working, please check out this video:
https://vimeo.com/669753660/de8b3c3d4f
To attach multiple files, add rows in the table by clicking the + icon. In each row you can upload a file like explained in the steps 1. - 5. above.