Greetings. My name is Anis. I'll be glad to help you today.
It appears that the Realtek Audio manager has got uninstalled and you want to install it back.
Let me know inform you that Realtek Audio Manager Software has been discontinued.
However, the old version still may be available at the manufacturer's website.
You can download it from your PC manufacture's website.
Alternatively, if you let me know the exact model number of your laptop (Motherboard, if it is a desktop) I can fetch the Realtek driver utility for you.