First of all we gotta get the mods a website where i personally get the mods is MODDB

This is how the website looks

Well is very simple all you gotta do is install the mods from the website moddb and then extract files anywhere you can find them

After that you gotta add the folder in the half-life files like in this photo

You did all of those? GOOD NOW CREATE A SHORTCUT TO HALF-LIFE AND NAME IT WHATEVER YOU WANT

Right click the shortcut and then enter at TARGET this command -game (MOD FOLDER NAME)