How to init connection with a Cisco over serial & minicom?

Trying to connect to a Cisco router, in purpose to learn Cisco skills that could help me finding a job. So, I plugged a cable in the rj45 Console (blue) port of a Cisco 888 router, and other end into serial port. On Debian 10, I installed minicom, then searched for serial tty:

sudo dmesg | grep tty
[    0.108074] console [tty0] enabled
[    4.648840] 00:02: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    4.669401] 00:03: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A

So I set up minicom to use /dev/ttyS0 , with 9600 bauds/8N1, and saved this configuation as cisco.
However, when launching sudo minicom cisco, nothing particular happens:

Welcome to minicom 2.7.1

OPTIONS: I18n
Compiled on May  6 2018, 08:43:56.
Port /dev/ttyS0, 09:17:07

Press CTRL-A Z for help on special keys


CTRL-A Z for help | 9600 8N1 | NOR | Minicom 2.7.1 | VT102 | Offline | ttyS0

Tried to reset the router (with the physical button), restarting it, unplug and replug the serial cable… but nothing happened.

==> How to initiate communication with the router ? Isn’t it automatically launching a terminal when connecting to it over serial console cable ?