If the xxxxxs are placeholders for your data, try something like:
'examplesite.typeform.com/to/nk19Yv?source='&{Source Field}&'signup_email_address='&{Email Field}&'referrer_email_address='&{Email Field 2}
Essentially, plain text goes between ‘quotation marks’, field references are between {curly braces}, and every grouping is joined by an ampersand (&). You could also try the CONCATENATE()
function.