Go to your Facebook Ads Manager: 

https://www.facebook.com/ads/manage/powereditor/manage/ads

Make sure you are viewing your "Ads" by most recent.

Click on the ad campaign you want to test:

Click the "Preview" button.

In the window that pops up, click the "Share" icon in the top right and select the "Preview Message" option.

This will automatically send your personal account the custom message that you have set up from the page.

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