The capability for multiple LDAP servers is now a standard part of ALM since version 12.5x and later versions have been introduced. The thing you would need is a user account for accessing the data from your LDAP system that has enough credentials to be able to access and poll that data, your LDAP admin team can create such a user with then grant the necessary credentials. I would recommend that one be created for this specific purpose with a non-expiring password rather than use a normal admin user account, as should something change with their credentials or password the LDAP authentication for other users will fail until the time that is corrected and it can be more involved to get rectified so it is easier to start with the recommended user account from the beginning.
The ADMIN guide has a section that pertains to Setting up LDAP and importing users through LDAP, for multiple servers you would just need to create each LDAP server within the site admin as you would create a single LDAP connection. As to the settings, these are specific to each individual LDAP server and system and your LDAP administrators can provide you with the necessary information.
Hope this helps,