Confirm email and password fields in WP-Members?

There is not functionality for that built-in at this time.

It may be possible to create some level of validation using the action wpmem_pre_register_data, which occurs after WP-Members does its form validation, but before the user is inserted.

Alternatively, this is something that is on the project list and will probably be added in either the 2.8 or 2.9 release (there will probably be a 2.7.5 before that).

Hello,
Could you please tell me where the action wpmem_pre_register_data should be placed in order to create a password validation field?
Thank you very much.

Any action or filter hook can go into your theme’s functions.php file, similar to using any other WP hook.