Click "Merge Customers"

Click "Keep This Record" on the primary profile that should be kept.

Click "MERGE THIS DUPLICATE RECORD" this will complete the merge and open the opportunity.

Click on the three blue dots on the secondary opportunity you would like to move into the primary opportunity.

You will then make sure the correct opportunity is selected. You should select the one you would like to keep as the main opportunity. Then press "Merge Record"