converting openssh key to dropbear and following your instructions from client or server side????

I am a complete NOOB and have been fighting this for a couple weeks.
I have OpenSSH working.
have installed dropbear

to follow your instructions,
can you clarify which is Server-Side and which is Client side. (I am trying to set this up using the OpenSSH I already have running and am unsure where to input your commands.) *This way I can cut and paste your commands or scripts, because Server side where dropbear is installed does not have a GUI

Secondly. I have OpenSSH working already and would like to use same keys so that I don't have any HOST errors when log into Dropbear on a boot or reboot.

Thank you for your help and patience in helping with this matter.