Dear aspirant

You can put anyway you want, but it should be clear and visible, deep your thumb in ink pad preferably blue colour once and put in the box provided. Just put once don't try to do again even if it's somewhat light it may cause overlapping so avoid to do more the once.

Mostly it's preferable to put thumb impression as horizontal if space is enough otherwise if vertical space is more you can put vertically also, there's no issues in that.

Today's your exam, do your best

All the best