Starting up Armbian on your Banana Pi (BP) for the first time....

Once you connect your BP via ethernet to your network, your BP will be issued with an IP address by the DHCP server of your router. You may need to look inside the router to find this IP address; look at "connected devices" (or similar).

Once you know the IP address, and using PuTTY (a free SSH client - download from here), enter this IP address into Host Name box and log into the BP.
The basic, pre-set, root username/password is root/1234
You will immediately be asked to change the root password so enter a new root password (twice).
You will then be asked for a user name and for a user password. Enter these, these being the normal ones you will be using to login to the Pi
You will also be asked for some additional info like group name, room number, phone number etc. None of this is mandatory so it's OK to press enter for each one. 

 Now you have your own username and password it is strongly advised to disable root login.

To do this (whilst logged in as root) ....

 $ nano /etc/ssh/sshd_config

Find this section in the file, containing the line with “PermitRootLogin” in it....

change PermitRootLogin yes to PermitRootLogin no

 $ sudo reboot 

 Now set your location, time, date etc...
 $ dpkg-reconfigure tzdata
and follow the instructions

Next it's a good time to update and upgrade your OS...
 $  sudo apt-get update
and once finished
 $  sudo apt-get upgrade (repeat if not all upgrades completed OK)

Since I have several Banana Pis on my network, I wish to distinguish between them. You can change the name (called system Hostname) of your Pi...
$  sudo nmtui
This runs a convenient little macro where you choose 'Set system hostname' and type in your chosen name.

Once complete,  sudo reboot 

 Next, it's probably a good idea to give your BP a static IP address as this makes login through PuTTY easier - and is essential if you wish to host web sites on the Pi...
$  sudo nano /etc/network/interfaces

add # to beginning of line:
  iface eth0 inet dhcp
to read
 #iface eth0 inet dhcp  
and add the following lines, usually before any reference to wlan (wireless lan):
 iface eth0 inet static

Of course, the address and Gateway addresses are to suit your network
(the last line isn't necessary, I just like to use OpenDNS DNS servers)

$  sudo reboot 

 This is your BP basically setup. It's advisable to occasionally login and run update and upgrade to keep all the software up to date...

 $  sudo apt-get update
and once finished
 $  sudo apt-get upgrade 

You may also wish to consider taking the SD card out, placing it into a PC and saving your new version of the OS as an image. This means running Win32 Disk Imager again but this time use Read insted of Write.