Guide

1. Head over to the profile icon on the top right.

2. And click on Switch to Salesforce Classic.

3. Find Accounts in the menu bar on top.

4. Find Merge Accounts under the Tools column.

5. Search for the accounts you want to merge and click on the Find Accounts button.

6. Make sure the checkboxes next to the accounts are checked.

7. Hit Next.

8. You will see the account details of both accounts you selected on the next screen.

9. Hit the Merge button to merge both the accounts.