How to start game?

ok, this may seem like a real newbie question, but thats why im here
ok, ive just installed esf ( i have half life, game of the year edition and the latest half life patch ) esf installed into the sierra folder. I've gone into there and clicked on the icon esf and it just goes onto bitmap viewer and shows a pic of the icon, so anyone know what im doing wrong please please reply, thanks for reading

You must open half-life (with hl.exe in the sierra folder) and then click 'mod viewer' or something and then choose 'earth's special forces' mod and click activate. And then you can use multiplayer to play the game.

*i think it´s "custom game"*
Firefly

k, going to try that, thanks for the help