According to the rules:
How do I do that in this interface? I don't see anything about it on the wiki page. I can click on a die and then click on my workers pile, but that just adds workers.Worker tiles: These may be used at any time (a tile, once used, is returned to
the general supply) to adjust a die’s result up or down by 1. Changing a die’s
result from 1 to 6 or from 6 to 1 is also permitted and also costs one worker
tile. Players may use multiple tiles to change a die’s result multiple times.