Just like many other knowledge areas, the first process in the Resource Management knowledge area too, comes from the Planning process group and is called the Plan Resource Management Process. Below is the PG-KA mapping,

The major output of this process is a plan viz. Resource Management Plan. This plan basically defines the procedures of how you will estimate, acquire, manage and use both the team as well as the physical resources. Coming up with these procedures is exactly what the plan resource management process does. Additionally, it also establishes the approach and level of management effort required to manage project resources. Note that you may perform this process more than once if required at the predetermined points in the project.
Project Resources may include team members, supplies, materials, equipment, services and facilities. An effective resource planning must consider and plan for the availability of resources ensuring sufficient resources are available throughout.
Resources are obtained from either the organization’s internal assets or procured externally. As a Project Manager, you should also consider the possibility of different projects competing for the same resources at the same time and location. This is something we have previously discussed here
Check more articles on Resource Management