you can check the portal vSphere [V5.1] - VMware Learning . Those are small videos about certain topics...probably you find something that can help you to improve your network skills. Another good source is youtube. There you find a lot of good video-tutorials...
Nevertheless as a.p. already mentioned you need to attend an authorized VMware training (like the Install, configure & manage) to become a VCP...This class will give you the basic information about many topics of the VCP-exam.