How can I apply for the 10point or 5 point veteran preference?

Q. How do I claim Veterans' preference?
A. If you are claiming Veterans' preference, the following documentation must be submitted with your application. Failure to do so will result in not having Veterans' preference applied.

If you are claiming 5-Points Preference, the following must be submitted:

DD214, Certificate of Release or Discharge from Active Duty (must show your character of service upon discharge)
If you are claiming 10-Point Preference, the following must be submitted:

DD214, Certificate of Release or Discharge from Active Duty (must show your character of service upon discharge)
SF-15, Application for 10-Point Veterans' Preference (must be complete)
Letter from the VA Regional Office stating what your percentage of disability is. It is not necessary to send documentation of what your specific disabilities are.
Purple Heart recipients: Purple Heart must be listed on your DD214 or other official documentation.

Source: https://www.vaforvets.va.gov/vaforvets/FAQs.asp

It isn't something you apply for. You attach a copy of your dd214 to a federal employment application and that grants you a 5 point preference for federal jobs. If you have a VA disability rating of 30% or more, you attach that and you get a 10 point preference.