If you need to attach files to the card:
1. Click on the purple plus sign in the open card.
2. Click "Upload file" button in the right panel of the card;
3. Select the files you want to upload (you can select more than one);
4. Click OK, the files will be uploaded and will appear in a separate section "Files" of the card.
Or you can just drag and drop file directly to card.
To upload file from Dropbox, you should:
1. click on the "Add Dropbox file" button;
2. log in to DropBox;
3. select the necessary file and click OK.
DropBox files however will be available for viewing and download to anyone who has access to the card.
To upload file from Google Drive, you should:
1. click on the "Add Google Drive files" button;
2. log in to Google Drive;
3. select the desired file and click OK.
In the case of Google Drive, the file is not downloaded to the Kaiten from Google Drive, only the link to the file is added . If other users of your company do not have access to this file on Google Drive, they can not open it (they will be transferred to the page with request access to this file).