/**** Run this query to get the boundary time or your AWR report ****/
select snap_id,
  snap_level,
  to_char(begin_interval_time, 'dd/mm/yy hh24:mi:ss') begin
from
   dba_hist_snapshot
order by 1
desc;

/***
Result look like this :
1696	1	20/06/18 11:00:12
1695	1	20/06/18 10:30:11
1694	1	20/06/18 10:00:09
1693	1	20/06/18 09:30:08
1692	1	20/06/18 09:00:06
1691	1	20/06/18 08:30:05
1690	1	20/06/18 08:00:04
***/

/**** Get your Database Id ****/
select DBID from v$database;

/**** Get your AWR Report in HTML or text format ****/
/**** If you're not sure what to put as a second parameter set 1 ****/
SELECT
   output
FROM
   TABLE
   (dbms_workload_repository.awr_report_html
      (YOURDATABASEID,YOURDATABASEINSTANCE,FIRSTSNAPSHOT,SECONDSNAPSHOT )
   );
/**
Example to get the report as text :
SELECT
   output
FROM
   TABLE
   (dbms_workload_repository.awr_report_text
      (3518879357,1,1693,1694 )
   );

Example to export result as html (way easier to read) :
SELECT
   output
FROM
   TABLE
   (dbms_workload_repository.awr_report_html
      (3518879357,1,1693,1694 )
   );
-> Export result to file AWR.html
**/