orapwd - Oracle password file
Set REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE|SHARED in init.ora

Create a new password file in %ORACLE_HOME%\database (Windows), name of password file must be pwd.ora
cd %ORACLE_HOME%\database
orapwd file=pwd%ORACLE_SID%.ora entries=5

If the password file already exists:
orapwd file=pwdSID.ora entries=5 FORCE=Y

Grant SYSDBA/SYSOPER to users:
SQL> grant sysdba to sys;

Grant succeeded.

select * from V$PWFILE_USERS;

USERNAME                       SYSDB SYSOP SYSAS SYSBA SYSDG SYSKM     CON_ID
------------------------------ ----- ----- ----- ----- ----- ----- ----------
SYS                            TRUE  TRUE  FALSE FALSE FALSE FALSE          0