My answer to that question would be three parts:
1. Make sure that you agree on what success looks like, at the micro and macro levels.
2. Discuss what that person needs to achieve success for both of you - mentoring, training, tooling, access, time, money, whatever.
3. Frequently make sure they actually have what they need.
When people are regularly missing out on what you call success, you’ll probably get rid of them. When they’re missing out on what they call success, they’ll get rid of you by leaving. Don’t assume you’ve understood what they think success looks like until you’ve really discussed it with them individually.