Reusable Approval Workflow where you choose Approver From an Approver List

Hi All,

I am looking for a Sharepoint Designer 2013 “Reusable Approval Workflow” for “Document Libraries” with Dynamic Approver, meaning "The APPROVER" is chosen from an “Approver List” that can have many Approvers listed.

The workflow would be triggered when a New Document needs to be added to the Document Library or an existing document in the Library is modified and needs to be checked-in/released.

I’m fairly new at SharePoint, so would need something with instructions.

Thanks to all in advance.