Space bar is definitely best if you want to hide the translation until you try to translate it yourself and then see how well you did. If, however, you want the translation to always show then you can change it here. Scroll down to the section labeled review hints. if you want the full translation to show right away, then change the option labeled grammar hint to show. If you have nuance turned on too this might lead to your screen being very cluttered, to make it more manageable you can change the grammar hint order to translation first. This will let you see the full translation, but you can press space bar to also show the nuance.