Mapping your skills in Pocket Legends is easy!
First, tap on Menu and then select your avatar page:
Next, tap on your Skills tab and select "Map Skills to main display!" Ensure that you have at least 1 skill point in a skill before you try to map it:
Next simply tap on the skill and then tap on an empty space to the right:
When you are done, simply tap "Done" and then the back arrow button:
That's it! Ensue that you have your skills expanded by tapping the button on the top right of the screen: