Finally go it working. In HeidiSQL session manager:
Under Settings Tab
Network Type: MariaDB or MYSQL (SSH TUNNEL)
Hostname: 127.0.0.1 or localhost
//Use the command below to find the hostname for the user you want to use to connect.
mysql> SELECT user,host FROM mysql.user;
User: mysql username
Password: mysql password
Port: 3306 (default)
Under SSH Tab tunnel
plink.exe location: find in location of putty
SSH Host + Port: Your digitalocean server IP and port (default is 22)
Username: Username to access your server terminal
Password: If you use SSH key when accessing terminal, leave empty
plink.exe timeout: 4 (default)
Private Key file: Location of private key file .ppk
Local Port: 22 (Default)
This should now connect to the database.
There are some suggestions online to edit the /etc/mysql/my.cnf file and comment out the bind-address for it to connect but this should be for testing only as it allows connection from any IP address with the key, unless you change it to your client static IP address.
MYSQL Workbench is similar but convert .ppk keyfile to OPENSSH using Puttygen for it to log in if using SSH key file.