The replies have gone off topic and do not answer the OP's original question of 'Where to place the LDAP Certificate
Please post links for this issue like JonB
quite rightly posted but make the links LDAP on Windows related as references to Linux installs and associated paths would only serve to create confusion.
An SSL certificate for LDAP is only required if connecting via Secure Socket Layer.
Try setting up LDAP without a certificate first.
As advised by the XAMPP for Windows developer, please find instruction on the Internet for installing LDAP and a certificate if needed, as this subject is for individual readers and members to find their own solutions and is not directly related to the normal running of XAMPP for which this forum provides support.