For Salesforce Lightning

  • From setup, go to Object Manager and click Campaign. From the campaign layout, drag and drop the "Quick-Send" button, to the Salesforce Mobile and Lightning Experience action section and save it.

For Salesforce Classic

  • Click on Setup and click the "Customize" tab from the home list screen. Go to Page Layouts for Campaign and click Edit for "Campaign Layout". From the buttons section, Drag and drop the “Quick-Send” button to the Campaign detail section and Save it.