you got to attend one of following courses,
vSphere: Install, Configure, Manage [V6]
vSphere: Optimize & Scale [V6]
VMware vSphere: Fast Track [V6]
vSphere: Install, Configure, Manage [V6] On Demand
vSphere: Optimize and Scale [V6] On Demand (coming Soon)
vSphere: Design & Deploy (coming Soon)
and then move towards going for 2 separate exams.
1) https://mylearn.vmware.com/mgrReg/plan.cfm?plan=64179&ui=www_cert
2) VMware Certified Professional 6 – Data Center Virtualization Exam
among above two exams, 1) is your vSphere Foundation exam. your VCA doesn't count as Foundation in vSphere 6 VCP-DCV exam.