There are two ways to change status please find below steps:
Step 1: Go to left-hand-side menu -> "Recruitment" -> "My Applicants"
Step 2: In "Status" column you can change the status of that applicant as you wish.
OR
Step 1: Go to left-hand-side menu -> "Recruitment" -> "My Applicants"
Step 2: Click on the applicant you wish to change status and it will take you to his detail page.
Step 3: You will find status drop down from which you can change status (please refer attach screenshot for your reference).