It's a pill. Most people take 100mg I only take 25mg because it lowers blood pressure. Basically it's a diuretic and it binds to androgens so you get rid of excess androgens (testosterone), making you grow less hair. It also helps with gaining weight in the stomache, as well as acne.

Spironolactone in the treatment of polycystic ovary syndrome: effects on clinical features, insulin sensitivity and lipid profile. - PubMed - NCBI