SSH login for beginners.

I apologise for something asking something I know is well documented, but I can’t seem to get my head around this. I’ve read documentation, watched YouTube videos and followed along with Lynda all day but I’m not getting very far. I know this will take most people seconds.

I created ssh keys with puttygen. Added them to my DO and created a droplet. I can login in as root.

I want to create a new sudo and allow ssh access only. Disallow root login and have ssh login only.

I’ve tried adding new a secondary key to DO for my sudo but it won’t let me login as and the sudo user I created.

Could you please walk me through the line commands starting from logging in as root and key(s) added to my DigitalOcean account.

I know it’s just something stupid I’m doing wrong. I’ve tried generating keys via puttygen and via the terminal and I keep running into issues. When I edit the config file I see the options I should toggle/change are already in place presumably because I set my droplet up without a root password.

Should my public keys be put in the same folder or, or should each user have their public key in their own folder? Thank you!