Step 1: Log in to your account using cPanel
Step 2: Using the cPanel File Manager and then go to the directory where you installed WordPress.
Step 3: Usually, WordPress is in the public_html directory, but it may be in a subdirectory beneath the public_html directory instead.
Step 4: Using your preferred text editor, create a file named .maintenance.
Step 5: Make sure the filename begins with a period (.) or this procedure will not work.
Step 6: Copy the following code and then paste it into the .maintenance file:
< ?php $upgrading = time(); ? >
Step 7: Save the changes to the .maintenance file.
Step 8: Maintenance mode is now active for the site. To restore normal site operation, delete the .maintenance file.