execute : system custom-language import
 
system custom-language import
Use this command to import a custom language file from a TFTP server.
The web-based manager provides a downloadable template file. Go to System > Config > Advanced.
Syntax
execute system custom-language import <lang_name> <file_name> <tftp_server_ip>
<lang_name> - language name
<file_name> - the language file name
<tftp_server_ip> the TFTP server IP address