This is not how you do it, What you have to do is, you have to make a signup data holder
and make its association with Account. Now, when you click the submit button from the signup page
it should call a microflow, and create an Account, which then saves all your information in,
the System.account, You can even setup the user role for them as well.
Hope it helps!
Add a NPE SignUpDataHolder in you domain model..
On the signup page, add a data view, and set its data source to microflow, now in the microflow create the NPE.
refer to the image below..
Now configure your data view to look like this,
On the save button, call a microflow, which creates an account object and fill the data coming from your data view into that,
refer to the image below.
If you want to add roles also, then it could also be done. Just let me know!