The second thing to do would be to ask why only white makes are applying, and consider what (if anything) might be done to alter that. That might involve some changes at the company, but more likely would require changes in the broader society.
The third thing to do would be to note that essentially no serious advocate of DEI goes beyond the idea that an ideal scenario is on average having work place representation roughly match the distribution in some broader social unit. If you have 0% black people in that broader social unit, nobody but people trying to ridicule DEI would suggest that you need to work towards more black people.
The criteria for what characteristics are considered by DEI efforts in a given context will vary. Gender, religion, "race", language, age ... these are others are all valid things that you might want to try to even up in workplaces to match the broader social context.
But this is exactly what I mean. You can try to make the job and the company sound appealing to females and minorities. But let's say 99.9% of the population around you is white and you just don't happen to get any female candidates applying because the number of females with those skills that are currently looking for work in your area happens to be zero. You could do a bunch of footwork and ask lots of "why". But if your small-to-medium sized company chiefly want to execute on a specific business goal, their focus will be on shipping product, beating the competition, keeping customers and employees happy. Who has pockets deep enough to fix some broader societal problem? How much of the budget should they spend on that? Is it even their obligation? What do the investors think?
This type of wider social problem should be tackled and funded by government: any department with a role in employment, equality etc. Responsibility for social issues cannot be left to private, profit-driven companies.