If you have multiple SSH keys generated for different purposes (one for GitHub, one for server administration, etc...) you can specify which private key to use via config.
In ~/.ssh/config
you may have the following:
host github.com
HostName github.com
IdentityFile ~/.ssh/id_rsa.github
User <your PC user name (not GitHub user name)>
host digitalocean
HostName <your server IP>
IdentityFile ~/.ssh/id_rsa.digitalocean
User <your server user name>