To Enable/Disable Frequently Bought Together section you need to follow below steps:
Manual Process
To Enable/Disable you have to go to Shopify admin, click Sales Channel => Online Store => Customization => In Home Page drop down select Products => Click on Default Product => In Apps Section Click on Add block => In APPS click on Frequently block => In Title add and update heading => click on Save button on the top right corner.
Automatic Process
To Enable/Disable Cross sell/Upsell section, Click on Active App in Setting => In Apps click on Frequently block => In Title add and update heading => Click on Save button on the top right corner.