Once you have installed Debian you will want to add / change your sources list.
First go to here : Source List Generator.
Uncheck the box that says “Use deb.debian.org (Fast Server Select) service?” so you can then select your own country if needed. Check / uncheck all the boxes that you need / dont need, and at the bottom hit the “Generate” button.
Next open a konsole and log in as Root. This is done by entering SU <enter> and then enter your root password <enter>
Paste this line into konsole and press enter : apt install curl wget apt-transport-https dirmngr
Once that has been done enter the following, still as root :
Your sources list will now be displayed in either nano or gedit. Delete all the lines in the file, copy the generated sources list on the website, and paste into your sources list. Then save the file.
At the bottom of the source list generator site will be the commands for getting the repo GPG keys. Copy each line and paste into the konsole, pressing enter after each. Once done enter “apt-get update”
You can also enter “apt-get upgrade” which will upgrade Debian if a new point release or version has been released.
A decent package manager for Debian is “Synaptic”, which I dont think gets installed by default. This can be installed by typing in a konsole (as root) : “apt-get install synaptic”
More to be added.