Hi @mscroggin , welcome to the Auth0 community,
I recommend taking a look at this post on our forum - How to configure additional signup fields on the Universal Login Page.
You’ll also find further examples of code here that you can use as a template for those additional fields you need - Lock Configuration Options.
The user will be redirected back to the redirect_uri that was passed as an Authentication Parameter when you make the /authorize call from your application, so you can specify the URL you want to redirect back to there and also remember to add the URL into the “Allowed Callback URLs” in your Auth0 tenant application.
Hope this all helps!