How to Add the Campaign Related List to the Account Page in Salesforce Lightning

This functionality is only available in the Lightning Experience user interface.

To add Campaigns related list to Account, please follow below click path:
Setup | Object Manager | Account | Page Layouts | Look for Campaigns under the related lists part and then drag it | Save the page layout.

 

To add Accounts related list to Campaign, please follow below click path:
Setup | Object Manager | Campaign | Page Layouts | Look for Accounts under the related lists part and then drag it | Save the page layout.