How to get AWR report as html file?

Generate Snapshots
SQL> EXEC DBMS_WORKLOAD_REPOSITORY.create_snapshot;
-> Run this SQL as twice (at the begin and at the end)

Get Automatic Workload Repository (AWR) as HTML format
Login -> Targets -> Databases -> Click Database -> Performance -> AWR -> AWR Report -> Select By Snapshot -> Click Generate Report -> Click Save to File -> Done :)