put this line in your server cfg

set sv_privatepassword "whatever"

then when you want to get onto the server you type in the console
/connect
/set password whatever
/reconnect

....u may not need the first step...and perhaps just set the password then connect....its the way i was first told , and its just a habit...

...and dont forget to put in a rconpassword

set rconpassword "whatever" is the line to put in your server cfg

then when in the game drop the console and type

/set rconpassword whatever

i think he whant an lockhed server so set g_password bla bla g_needpass 1 conect to the server and type in the console /password bla bla