When you have selected Skills in the menu, the window containing the list of characters in your group becomes active for you to select the character you want to see the list of skills.
You can select the character whose abilities interest you by using arrow keys and validate your choice by pressing the enter key or clicking on it.
Once the character is selected, the list of his skills is displayed sorted by category.
The category you are interested in can be selected using arrow keys or clicking on it.
If you want to go back, simply press the escape key.
Some skills are usable in the context of the menu.
They are displayed in white.
The others are not usable here.
They are displayed in grey.
In the current version of the game, there is no usable skill from the menu.
They are all used either in combat or in a particular environment by exploring the map.
(No, you can capture no chicken if there are none nearby.)