Change default credentials

Password

You can leave the username as it comes, i.e. pi. However, I will obviously change the password. This can be done with the command passwd.
Shell
passwd
Raspberry Pi: Default Password & How To Change, shellhacks.com, May 7th 2020

Hostname

Use the system tool raspi-config to edit the hostname.
Shell
raspi-config
How to Change Your Raspberry Pi's Hostname, tomshardware.com, May 1st 2020