[Act] How to modify user's Main page to add new options

[Víctor Manuel Rivas Santos]

Hi everyone,

We want to add the possibility for those attendants to YAPC::Europe 2015 
who need it of asking for an introductory letter so that they can obtain 
the corresponding visa in their countries.

I was thinking about modifying the user's Main private page... and, 
sorry, but I can not find where the template for this page is. Any 
suggestion, please?

I have been recursively "grep-ing" the directory containing the whole 
site, and could find nothing, so, any help will be welcome.

Thanks!
Victor