1) I would first feel out your ideal persona better. You could do this by posting questions on forums where managers hang out (e.g. www.reddit.com/r/askmanagement/). Ask if people on the forum would potentially be interested in your product, and if not, why not. Be totally open to and appreciative of any suggestions given.

2) You could then better do targeted advertising with
A) Google Adwords: choose keywords that managers would use when searching for solutions to the problem that your product fixes.
B) Facebook: choose your manager persona in the user-friendly Facebook ad design interface.
C) other online targeted advertising

_Before_ you do advertising, make sure you have analytics set up for your website so you can accurately track who's coming from which ad, and how far each gets through your funnel. If you don't have much technical skills, the best option might be to use Popcorn Metrics (popcornmetrics.com) coupled with Mixpanel (mixpanel.com).