doubt about: trigger, trace

Hi,

1_somebody to helpme on: trace?

2_I need to create the trigger:

how to do so?

create or replace trigger logon_trigger

after logon on database
begin
if (user = 'USU1' ) then
execute immediate 'ALTER SESSION SET TRACEFILE_IDENTIFIER=''USU1_APP''';
execute immediate 'alter session set timed_statistics=true';
execute immediate 'ALTER SESSION SET EVENTS ''10046 TRACE NAME CONTEXT FOREVER, LEVEL 12''';
end if;
exception
when others then
null;
end;
end;

3_how todo with sqldeveloper?

this apply all dba user:USU1?, if yes so how to apply only 1 user jdeID?

great thanks!