Try to give first:
cd /var/discourse
And after that ./discourse-doctor
I’m almost sure your email-issue is because you have not installed any service for email delivering.
There is quite lot of things you have to setup on droplet. One-click installing for VPS and Discourse is just starting point.
Console of droplet is just for emergency situation, when PuTTY or something else breaks. But login using PuTTY and give then
wget -qO- https://repos-droplet.digitalocean.com/install.sh | sudo bash
It doesn’t matter where in all directories you are at that point.