Adding skills starts in Configuration/Skills. There, using the "Add a skill" button, you will be redirected to a page that allows you to create a skill.
First of all, you need to name the skill and choose if it's a soft or a hard one. With a soft skill you have to decide if it's gonna be graded manually or by an average value of behaviors that define the skill.
You can also decide if this skill is going to be measured with default scale or if you want to use your own.
When the skill is added and if it's a soft one, you have to define behaviors. Just go to the "Behaviors" tab and click on "Add a behavior" button.
Behaviors are being defined exactly the same way as skill - you name them and choose a scale - default one or your own.