Here is a step-by-step guide that explains how you can enable Single Sign On for your WordPress website:
Step 1: Create an account on WordPress.com using this link. Skip this step if you already have an account. You may be required to create a dummy blog on wordpress.com as part of the registration process.
Step 2: Once your account is created, click here to enable two-factor authentication. Specify your phone number, WordPress will send a verification code via SMS and you need to type the same code to verify your number.
Step 3: Go to your WordPress blog, install the Jetpack plugin, activate the plugin and then click the green button that says “Connect to WordPress.com” to link your blog to your WordPress account.
Step 4: Once the connection is established, go to Jetpack settings and activate the “Single Sign On” module.
Step 5: Go to your WordPress installation folder via FTP or SSH, switch to the current theme folder