You need to first create at least one group and then you will add a filter to that group.
This will bring up another box to the right hand side where you can add filters.
When you go to this section for the first time it will say “You don’t have any custom filters yet.”Press CTRL+R, which is a toggle to show or hide the filters.
In the Adblock Plus Filter Preferences window click the Custom Filters tab.
Another method to get to the filters is the CTRL+SHIFT+F key combination.
Click the ADP icon -> Filter preferences, or on Firefox main menu click Tools -> Adblock Plus -> Filter preferences.
Install the Adblock add-on for Firefox.
Use Adblock Plus to Remove “Stay signed in” Box Here’s what I do to get rid of this box by default. One solution that I have found is to use Adblock Plus.