To set up static IP on your cube do the following.

SSH into the miner with user/pass: baikal/baikal

The command below opens a text editor for the file you want to modify:
sudo nano /etc/network/interfaces

Add some lines like what I have in the code box below (modified accordingly for your network).  I added these below the line that starts with "source-directory" and above the lines that all start with the # symbol.

Hit ctrl+x to exit the editor

It will ask you if you want to save, hit y to save

It will ask you for the file name but it will default to the one you are already editing so just hit the enter key to confirm the default

At this point you can run "sudo nano /etc/network/interfaces" again to confirm the file now contains your changes if you want, but if you did everything correctly you don't need to.  Restart the miner with the power switch and it will come up on the new static IP.

BTW, it seems likely that with the appropriate changes made in that file you could also enable and configure the wifi and use the miner wirelessly.