How to install something on Ubuntu-core?

I have installed Ubuntu-core +Qt on nanopi-m1 board but there is no
terminal to install something on it! How can I do that?

What tools do you use to connect to the development board? Through the
network or serial port?

Oh my GOD!
I didn't think there is an answer here! Sory for delay

Nothing! I am newbie to Ubuntu core and it was a question for me, how can I
do something on it? May you explain more?

I have this connector(TTL to USB):

 But didn't use it since now! Can I use this instead of "PSU-ONECOM" ?

What about network mode? I shoild use SSH? How? can you explain more?

Are there any difference between network and Serial mode in results?

or districtions