To connect your Facebook Pages to Postcron click on the + sign button at the top right side of the screen, and then choose Facebook.
If you are already logged into your Facebook personal profile, you'll be shown a list of the business pages this profile manages. However, if you aren't, you will be prompted to log in. Make sure you log into a profile that has an admin role on the page you're looking to connect.
Then, choose the Pages tab and you'll see all your Pages listed; you just have to click on the + sign button next to each Page you want to add. Click here if any of your Pages isn't listed.
Postcron will request that you accept publishing permissions in order to post to those social accounts on your behalf. Make sure you accept all of them to avoid future publishing problems.