tailwind apply directive is not working tailwind

I have installed tailwind successfully in my machine and used it to perform some tasks. Now when it comes to using the @apply, things are not working. I have copied some styles used earlier and tried to use in the @apply but with no success kindly assist

'''
<body class="bg-gray-600">

@import "tailwindcss/base";

@import "tailwindcss/components";
.body{
    @apply bg-gray-600;
  }

@import "tailwindcss/utilities";


 <body class="body">
'''

Then I have built the script, but the background style is not applied