If you've installed Kaizena Shortcut, you can also add a file to Kaizena from Google Drive.
In Google Drive, right click the file, click "Open With," then click "Kaizena":
If you haven't added this file to Kaizena before, you can choose a group:
...and then a conversation:
When you've selected the conversation, the file will be added and you'll be taken to that conversation.
Updating or Finding a File
If you've added this file to a conversation before, you have a choice:
If you "Add or Update" the file, you can choose a group and conversation just like you did before.
If you want to find this file, you can select the group and conversation from the conversation where the file has already been added.