I am trying to set up link my RStudio with GitHub
in options > Git/SVN > i click create RSA key. However, i don't know what my passphrase or password is or should be.
Have you seen https://happygitwithr.com/? Among other things, it walks you through all the steps of connecting RStudio with GitHub for the first time, and your various authentication options. Highly recommended!
I'm not following you, the passphrase is optional and even if you want to use it, is defined by you. What error message do you get when you try to create the key leaving both text boxes empty?