Facebook allows only Facebook Pages and Groups to be connected to third party apps, such as Hookle, and personal Facebook Profiles cannot be connected.
Thus, you need to have or create a Page under your Facebook Profile to connect it to Hookle.
Tip: You can create as many Pages as you want under your Profile and they're completely free!
Before you connect
Make sure that your Facebook has a Page role of Admin or Editor. You can do this on the Facebook Page or through Facebook Business Manager. See Manage Page Settings in the Facebook help center.
If someone else have given you Admin role to a Page you need to accept the invitation by logging in www.facebook.com on your computer as the invitation might not be visible in Facebook mobile.
See instructions how to connect Facebook Groups.
Connect Facebook Page to Hookle
Open Hookle app and go to the Profile -> Accounts -> Connect new account.
Select Facebook. Then accept all desired permissions (Facebook will ask for certain permissions) and select the Facebook Page(s) you want to connect to Hookle.
Problems with connecting?
The browser might remember credentials of your previously logged accounts. Thus, make sure you authenticate and reconnect accounts with right credentials if you connect Pages from multiple different Facebook Profiles to Hookle. If there is credentials of another account while you authenticate, open your browser to logout from your Facebook and then try authentication again in Hookle.
Troubleshoot Facebook connection and publishing related issues.