When to use it
Use it when you hand off a task. Say who owns it, when it's due, and ask what support they need. If you say “if you have time,” it will probably get done whenever there's time, which may be never.
Example
You: “I'd like you to own the vendor report. It's due Friday. What do you need from me?”
Teammate: “Access to last quarter's numbers.”
You: “I'll send them today.”
In an email or Slack message
Confirm in writing: “You're owning the vendor report, due Friday. I'll send last quarter's numbers today. Let me know if anything else would help.”