You can use connect( userConfigFile, userKeyFile, adminServerName, timeout ).

userConfigFile: Name and location of a user configuration file wich contains an encripted user name and password.

userKeyFile: Name and location of the key file that is associated with the specified user configuration file and is used to decrypt it.

See help('storeUserConfig'):

wls:/offline> help('storeUserConfig')

Description: 


Creates a user configuration file and an associated key file. The user 
configuration file contains an encrypted username and password. The key 
file contains a secret key that is used to encrypt and decrypt the      
username and password.                                                  
                                                                        
Only the key file that originally encrypted the username and password   
can be used to decrypt the values. If you lose the key file, you must   
create a new user configuration and key file pair.                      
                                                                        
In the event of an error, the command returns a WLSTException.          

Syntax:

storeUserConfig([userConfigFile], [userKeyFile], [nm])
- userConfigFile = optional. Name of the file to store the user configuration.
 The filename can be absolute or relative to the directory from which
 you enter the command. If not specified, the user-configuration file
 directory defaults to the JVM user-home directory. This directory value
 varies depending upon the SDK and type of operating system. The filename
 defaults to the operating system username prepended to
 WebLogicConfig.properties. For example, username-WebLogicConfig.properties.

- userKeyFile = optional. Name of the file to store the key information
 that is associated with the user configuration file that you specify.
 The pathname can be absolute or relative to the directory from which you
 enter the command. If not specified, the key file directory defaults
 to the JVM user-home directory. This directory value varies depending
 upon the SDK and type of operating system. The filename defaults to the
 operating system username prepended to WebLogicKey.properties. For example,
 username-WebLogicKey.properties.

- nm = Optional. Boolean value specifying whether to store the username
 and password for Node Manager or WebLogic Server. If set to true,
 the Node Manager username and password is stored. This argument
 default to false.

Example:


wls:/mydomain/serverConfig>  storeUserConfig('c:/myFiles/myuserconfigfile.secure', 'c:/myFiles/myuserkeyfile.secure')
Creating the key file can reduce the security of your system if it is
not kept in a secured location after it is created. Do you want to
create the key file? y or n
y
The username and password that were used for this current WLS
connection are stored in c:/myFiles/mysuserconfigfile.secure and
c:/myFiles/myuserkeyfile.secure
wls:/mydomain/serverConfig>