I have noticed that if you add a custom feature (I'm assuming this is what you're talking about) you need to have at least one feature setting defined in order to see the 'settings' link above the feature when you are logged in. In this case, you can click on the page settings where you have the feature displayed, select the feature name in the pane where it is configured, then click the gear icon to the lower right of the pane box and that will bring you to the settings for the feature. From there you can click on the 'Security' tab and set permissions.  Otherwise, you can click on 'Content Manager' in the Admin screen, then click on 'Publish/Edit' for the feature and the gears icon at the top of the page there will also link to the settings for the feature.