Installing Closet System (Wire)

Two of my closets had wire closet organizers (metal and plastic) which ripped out when I added weight to them.  They were not attached to studs, just tacked into the drywall.  I'd like to reattach them so I can start hanging my clothes again, but I'd like some help figuring out how to secure them so they don't rip out again.  I don't think it would take long, and whatever other supplies I need we can get at the Home Depot 10 minutes away.  Let me know if you're willing to help!