Options (LOADERCLI) 
When
you call the SAP DB Loader with
the SAP DB Loader CLI (LOADERCLI), you can specify a number of options for the
SAP DB Loader. For a list of all possible options, see SAP DB
Loader: SAP DB 7.4, Section
Options.
To
connect to the database instance on the local server, you must enter at least
option -d <database_name>.
In addition, you
must specify the name of a
command file in
option -b
<command_file>.

You want to specify the following user data as options: database user and the name of the database instance
loadercli -u samplename,secret -d TST -b command.dat
The Loader is called and a database session is created for the database user samplename, password secret, with the database instance TST. All further commands statements can be found in command file command.dat.