Sure.
First open the States tab in the database. Then locate the Note text box in the bottom right hand corner of the window. All you have to do then is insert the <slip> tag adding in the desired slip damage effect. I've provided a picture to show some examples.
To provide some additional information, I'll explain what information you can provide.
<slip HP -100> for example, causes the state to reduce HP by 100 every turn. In order to make it heal 100 HP every turn, you change the - to a +. So you'd type in <slip HP +100> in order to do that.
In the other example, <slip HP -10, 5> will make the actor lose 10 HP every 5 steps they take on the map/field, as well as lose 10 HP every turn they take in battle. You can do the same as above to regenerate HP every x amount of steps.
Similarly, you can change HP to MP to have the same effect but on the actors MP instead of HP. So <slip MP -1, 1> makes the actor lose 1 MP every 1 steps on the map/field or each turn in battle.
You don't have to set the "Slip Damage" tag to on in order for the script to work either. Having it on or off has no effect on what happens as the script overwrites it anyway. Just having the tag in the Note section is sufficient.
Hope that helps a little. You can find the info on how to use the script on the script itself under the section titled "Instructions for Usage" if you need a reminder on how you set out the text tag.