Publisher actions are available in Salesforce 1 and Lightning Experience, and these are object-specific and available on the Object Detail Lightning page.

To create a publisher action, you can use the Object Manager tab from the Setup menu. The navigation path is Setup | Object Manager | <select object>| Buttons, Links, and Actions.

The following screenshot shows how you can create a publisher action for an Account object using a custom Lightning Component:

The Publisher Action also needs to be configured based on the page layout. This can be achieved via Object Manager. The following screenshot shows how you can configure a custom publisher action: