How do I properly use my viper orbs

I’ve been playing for about a year, and I’m currently bronze. I unlocked viper last night and played a couple of games with her in comp, and got a good feel for the agent. I figured out some good walls and i top fragged both games. The problem is that I never have any idea what to do with my orb. it ends up not being used most of the time, unless we’ve planted spike and I can use it to keep people off by combining it with Molly. Where should I be using my orbs, especially on defense?