Hello,
Your lucky i'm checking the forum today (i do it every 3/5 days in general...)..
(note: for a faster and priority support, there's pro subscriptions
)
So, you can create custom fields overrides for each core registration fields, but, as you want just to change the label, you can use the languages strings override system of Joomla.
Check this short tutorial here first :
icagenda.joomlic.com/docs/documentation/...joomla-administrator (a very usefull tool!)
Then, search in your admin language override for this string (in site) : ICAGENDA_REGISTRATION_FORM_NAME
Best Regards,
Cyril