After opening up the Argo app, you can choose to sign in using one of 4 methods: Apple, Google, Facebook or Email. Upon signing in for the first time an account will be set up linked to your email address. You should use the same method/email address each time. Signing in using a different method/email address will establish another account.
Note: Signing in via Email Sign In requires you to enter account information along with receiving and accepting a confirmation email.