CCNA Security is not one of the "skip training" certifications. You either need to be VCP certified in another area or have a CCNA Datacenter, CCNA R&S or CCNP Datacenter, CCNP R&S (the Cisco certs "skip" runs till 25 Feb 2015).
So either you would need to follow the training or you could go for one of the other CCNA certs to be eligible for directly taking the exam.