Clarify the first step: authentication

README.md

@@ -34,6 +34,8 @@ Requirements: Python 3.8+.
 ```python
 import gspread
 
+# First you need access to the Google API. Based on the route you
+# chose in Step 1, call either service_account(), oauth() or api_key().
 gc = gspread.service_account()
 
 # Open a sheet from a spreadsheet in one go

docs/oauth2.rst

@@ -1,11 +1,20 @@
 Authentication
 ==============
 
-To access spreadsheets via Google Sheets API you need to authenticate and authorize your application.
+To access spreadsheets your application needs to authenticate itself with the Google Sheets API. Choose from the following options.
+
+#. Create an :ref:`API key <api-key>` if you’d like to only open public spreadsheets.
+#. (or) Create a :ref:`OAuth Client ID <oauth-client-id>` if you’d like to access spreadsheets on behalf of end users (including yourself).
+
+   - When your application runs, it will prompt the user to authorize it.
+
+#. (or) Create a :ref:`Service Account <service-account>` to access spreadsheets as a standalone bot.
+
+   - Service accounts get their own email address, so can be authorized by sharing the Sheet with the account in the same way it is shared with a person.
+   - Service accounts don't need any explicit permissions to access Sheets that are shared to "anyone with the URL".
+
+An API Key is the easiest option, but to access private Sheets you need authorization. To provide that interactively, use an OAuth Client ID. To pre-configure authorization, use a Service Account.
 
-* If you plan to access spreadsheets on behalf of a bot account use :ref:`Service Account <service-account>`.
-* If you'd like to access spreadsheets on behalf of end users (including yourself) use :ref:`OAuth Client ID <oauth-client-id>`.
-* If you'd like to **only** open public spreadsheets use :ref:`API key <api-key>`
 
 .. _enable-api-access: