The vaccine is available after an exposure or potential exposure ("post-exposure prophylaxis"). CDC recommends that the vaccine be given within 4 days from the date of exposure for the best chance to prevent onset of the disease. If given between 4 and 14 days after the date of exposure, vaccination may reduce the symptoms of disease, but may not prevent the disease.
Vaccine supply is currently extremely limited. Finding a vaccine is difficult right now, but it can be done.
Because there are limited supplies of the preferred vaccine, and because the outbreak is not considered endemic, other temporary interventions to reduce spread (limiting skin-to-skin and sexual contact, covering skin at parties, going to less crowded spaces) are also helpful to reduce risk.
Because vaccine supply is currently so limited, receiving one can come down to being lucky enough to hear about a "pop up" from social media.