to add the console. go to your half-life folder and look for this icon
When you found it, Right click on it and select
create shortcut like this:
now look for this icon and name:
Then right click on it and
select propeties:
now you did that. you will see something like this
see the red circel? add -console there and press APPLY. now go into the game and use the ~ button to use console. that button is JUST under your ESC button and LEFT to the 1 button