under Iranian constitution, how a president-elect is endorsed by the leader ?

ID: 48527 | Date: 2017/08/05
Under Iran’s election law, the president-elect is required to gain the Leader’s official approval before being sworn in before the Parliament (Majlis).

The leader gives his official approval for the president-elect by giving him a decree to assign him his duties. 

This process, called Tanfiz (validation), the Leader affirms the outcome of the presidential election.