Being self-hosted you will need an smtp provider.
Has a free tier of 300 messages/day. SMTP account on this one is the email you signed up with and the password is your account password.
As lilly has mentioned and provided links to the official install instructions
But to give you an easier answer to connecting to your domain.
You will need to setup a DNA record on your domain server.
This is an ‘A’ record the first is the subdomain name ie “community” the data is your VPs server ip address.
This is in the official install instructions however at times ppl miss this