Here is how to limit idle timeout for user USER1.

SQL> alter system set resource_limit=true scope=both;

System altered. 

SQL> create profile user1_profile limit idle_time 60;

Profile created. 

SQL> select profile from dba_users where username = 'USER1';

PROFILE
------------------------------
DEFAULT

SQL> alter user USER1 profile USER1_PROFILE; 

User altered. 

SQL>

You can query DBA_PROFILES to looks at the settings of the profiles.