Dear Mrunali
To give u a summarized view on this HR play a vital role in strategy formulation which begin with strategic analysis stage where they identify business goals, external opportunities and competitive advantages. they are also expected to environmental scanning to identify the people-related business issues, further HR must play a role in clarifying performance expectations and future management methods. At this stage a business mission is determined and action plans and resource allocations are set. HR strategies, objectives and action plans must be set to coincide with and ensure the business strategy is carried out.
Then comes the step of implementation.
Also, I have got a document on this, please check.