As a first step, you can download Debian on https://www.debian.org/distrib/netinst

1. Select Graphical install :

2. Select your installation language :

3. Select your geographical area:

4. Configure your keyboard :

5. Give your server a name:

6. Enter a domain or leave blank if you don't have one:

7. Enter a password for the root user :

8. Create your first user :

9. Choose a login :

10. Choose a password :

11. Select partitioning Assisted - use an entire disk :

12. Then select the disk where Debian 12 will be installed:

13. Select the option All in one partition :

14. Select Complete partitioning and apply changes :

15. Confirm with Yes :

16. Select No :

17. Select the country in which the mirror is located:

18. Select a mirror, usually deb.debian.org is a good choice:

19. Enter a proxy, leave blank if you don't have one:

20. Choose whether you want to take part in the statistics study:

21. Uncheck all and leave only SSH server :

22. Install GRUB on your main disk:

23. Select your drive :

24. Installation complete :

25. Your server starts :