Let me show you how it's done. I'll be demonstrating it on the Slack desktop app. However, you can also handle this process through the Slack web interface in the same way.
Integrating Google Drive and Slack
1. Open Slack
The first thing you must do is open Slack and then navigate to a workspace in which you have permission to install apps. If you don't have permission to install apps on your workspace, you can either request your admin to take care of it or request permission from your Slack admin.
2. Add the Google Drive app
From the Slack desktop application, navigate to the workspace in question and then scroll down to the Apps section in the left sidebar (Figure 1).
Click Add apps, and you should see Google Drive listed (Figure 2). If not, type Google Drive in the Search field near the top of the window.
Click the Google Drive button and then click App Homepage. This will take you to the Google Drive app page in your default browser. On that page, click "Authenticate your Google Drive account" (Figure 3).
Upon clicking to authenticate your Google Drive account, you'll be prompted to select the Google account to be used and to allow the required permissions for the app. As soon as you've authenticated your account, you'll receive an alert from Slack that you've added Google Drive to the workspace.
Using Google Drive in Slack
To use Google Drive in Slack, click the plus icon in any message field in the workspace. If you type Google in the resulting search field, you'll see the available options (Figure 4).
From that menu, you can create a new document, spreadsheet, or presentation within Google Drive or add a file from your Google Drive account. Click the entry you want and configure it how you want, and Slack will automatically open your default web browser to the new document you want to create in Google Drive.
If you opt to upload a previously created file from Google Drive, a pop-up window will appear (Figure 5), allowing you to navigate Google Drive and upload the file you require.
And that's all there is to adding Google Drive integration to Slack. If you depend on both of these services, do yourself a favor and integrate them immediately to make your daily workflow a bit more efficient.