I want to add more padding

Love your plugin but think it’s too tight between the labels and the instructions text and would like to change it to:

.visual-form-builder label, label.vfb-desc {
    padding-top: 5px;
}

but cannot make it work. I’m not good at coding but I’m learning fast so please let me know how I should do it to make it work even if the plugin is updated.

http://wordpress.org/plugins/visual-form-builder/