Adaptive staircase for onset of a dot

I am creating an experiment with two stimuli: a letter that is fixed and a white dot that appears on it after 1.5 seconds. I want the participants to be able to adjust the time at which the dot appears on the letter, by pressing left (for earlier onset of dot) or right (for later onset of dot).

I tried using the Interleaved staircase but I don’t know what conditions I need? There is no correct answer so I don’t now what I should do