If you want to add an agent for your store, please follow below steps –
Steps 1: Go to My Account -> Store then click on Managers tab.
Steps 2: To invite an user as agent, click on Invite Manager button.
Steps 3: Enter user email into input box then click on Add button (To invite as agent, need to register first).
Steps 4: User will get a verification email. Need to verify the invitation to include an user as agent.
Steps 5: After verify the invitation, he will be able to add listing for specific store. An user could not be agent for multiple store.
Note: When an user is treating as agent, not possible to manage his own listing and store.