There are several ways, all following the same trick – you have to enumerate all of the steps you want your slider to have.
Here's one way to do it:
*question: How are you?
*type: slider
*before: Lousy
*after: Great
*save: rating
1
2
3
4
5
6
That might be okay for six options, but if you had more you might want a more compact way to define the possible answers. Here's how:
>> scale = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
*question: How are you?
*type: slider
*answers: scale
*before: Lousy
*after: Great
*save: rating