You will receive an email to your email address that was entered when sharing a specific folder <<ensure the guests check their spam/junk folder!
Click 'open'
A Sharepoint tab window will pop up that requires you to submit a security code, this will be sent to your email address specified when sharing access was established.
Retrieve the code from your email <<<<ensure the guests check their spam/junk folder!
Enter code the select 'verify'
That's it!