A temporary inbox usually shows the address at the top and incoming messages below it. After generating an address, wait for the sender to deliver the message, then refresh the inbox. If the service supports automatic refresh, keep it enabled while waiting. Remember that temporary messages may be deleted automatically, so save information you are legitimately allowed to keep.
For practical use, always review the provider rules and avoid sharing sensitive information through temporary inboxes. A temporary address is best suited to low-risk, short-term interactions.