Generate ssh key:
ssh-keygen -t rsa -C "your-email-address" -f "github-username"
Example for personal github account bob and work github accound workerbob:
ssh-keygen -t rsa -C "bob@email.com" -f "github-bob"
ssh-keygen -t rsa -C "bob@workemail.com" -f "github-workerbob"