SPSearch4 is the service name for the SharePoint Foundation Search service. It is considered a best practice to run this service with an account other than the farm account. But where do you change it?
Usually you would change it in Central Administration > Security > Configure service accounts. But if you are reading this you probably have figured that SharePoint Foundation Search is not part of the available services you can pick on the list.
To configure the credentials you need to do it from here:
System Settings > Manage services on server > SharePoint Foundation Help Search