Support ? [Plugin: Pie Register] paypal button not showing

im trying to use the pie register plugin and im having trouble getting the actual paypal button to show up after people register.

this is what it looks like:

the only reason i can think that its doing this is because i didnt add this part of code:

“Please put this code at the top of your wp-login.php otherwise the plugin won’t work properly.
<?php
session_start(); ?>”

and i didnt add it because i dont have a login.php file.

does anyone know a way around this? id appreciate any help,

thanks.