Debian 12 Bookworm repository information

Here are the steps to add the main repository address to Debian 12.
Add to sources.list
Open the sources.list using your favourite text editor (e.g. Mousepad),

su
mousepad /etc/apt/sources.list

Copy and paste the following lines into the file,

deb https://deb.debian.org/debian/ bookworm main contrib non-free-firmware non-free
deb-src https://deb.debian.org/debian/ bookworm main contrib non-free-firmware non-free

Save and close the file. Update the repository list and upgrade the packages by applying following commands;

apt update
apt upgrade