The way you set up LDAP in CLM depends on some things like your application server. There are some jazz.net articles and deployment wiki topics that may get you started. You may want to explain a bit more about what you have done and what specifically is not working, since this is a pretty big topic.

Configuring CLM on WebSphere Application Server with LDAP
https://jazz.net/wiki/bin/view/Deployment/ConfigureCLMOnWASWithLDAP

Manually configuring the Apache Tomcat web container to use LDAP
http://www.ibm.com/support/knowledgecenter/SSCP65_5.0.2/com.ibm.jazz.install.doc/topics/t_manually_config_tomcat_ldap.html

1. Depends on whether you want to use ldap or ldaps.
2. Are you using (real) WAS.
3. If using (real) WAS, if you want to use federated repository.

For ldaps with WAS, you need to import the whole SSL certificate chain in to WAS, on top of the user dn and password. Documented somewhere.
If your ldap uses custom attributes for queries, you need to add configuration to WAS. Documented but requires a bit of digging. Don't know if liberty profiles handles that.
If you want to use federation for user lookup (specially if you want file based and ldap) you will need to map attribute to attribute class. Have seen WAS+LDAP experts done that. Have not been able to find documentation.