<ComboBox Grid.Row="2" Grid.Column="1" ItemsSource="{Binding Path=SkillItemSource}" SelectedItem="{Binding Path=neededSkill, Mode=TwoWay}" SelectedIndex="0" Margin="5" MinWidth="100"></ComboBox>

public Skill neededSkill = Skill.FirstSkill;

public string[] SkillItemSource
    {
        get
        {
            return Enum.GetNames(typeof(Skill));
        }
    }