the spindle *should* look like this
which allows you to line up the slots
and access the compression adjuster screws through the holes
If your bike came with non-adjustable forks and has had them upgraded, but not the spindle, you might need to modify or replace your spindle.
Easy enough to check your forks next time you have the front wheel out though.
While the Showas are adjustable, they're not a great design. The stock needles have too short a taper meaning the valves are fully open from a few clicks out and further adjustment makes little or no difference.