Good question.

The right hemisphere has language processing capacities, but it doesn't have language producing capacities.

So it can make sense of words, it just can't produce them.

The way you give the instruction to the right hemisphere and not the left is by putting the instructions in the left visual field (keeping the eyes fixed). This projects the image to the right half of each retina, which strangely only sends information to the right hemisphere (and vice versa).