Like i have to submit a leave application ist it get approved by the recommender after that by the approver there will be 3 approvers if ist one get approved then it should go for the 2nd then after the 3rd one
Search for the Workflow in Awesome Bar(search bar) and then create workflow for Leave Application.
You can read more about Workflow here.
https://docs.erpnext.com/docs/user/manual/en/workflows