Good day Shoyeb,
I am wondering what you need a document for? The clause 7.1.6 does not require documentation.
That said, typical approaches are job descriptions (which are documented) and change management (which is usually documented and very often includes a training component).
Some people keep a matrix listing personnel on one axis and skills on the other axis. We can think of that as a "skills library" that can be referenced when changes prompt a review of available "talent" and help managers plan to fill gaps. Changes include organizational changes (a key member is leaving) as well as new products/services, expansion, new regulatory requirements, new customers also bringing requirements, and business strategy such as reducing costs of errors or waste.
I hope this helps!