Ubuntu Core SSH Sign in and Inel NUC

Hi, I have installed Ubuntu core on Intel NUC and installation was successful. Can see that ssh mySSOAccount@ is visible on the Intel NUC.

Now I am an same network as 192.168.1.x, and would like to access the this newly installed NUC. Did SSH and message appears like this: “Authenticity of host can’t be established”. "This key is not known by other names. Are you sure you want to continue. " Selecting YES, it prompted me to enter the password of the (Intel NUC device), where I have no password for this device.

Note: Have created SSH key and SSO account as described here: