Learn Spanish (Latin America): Chicos, curen la herida y pónganle esta venda. - Guys, treat the wound and put this bandage on it.

Because pongan is an affirmative command (telling someone to do something). In Spanish, object pronouns like le must be attached directly to the end of an affirmative command, creating a single combined word.

Why is there an accent mark on pónganle?

When you attach a pronoun to a command, it adds an extra syllable to the word. The written accent mark is needed to keep the spoken stress on the original vowel. The standalone command is pronounced pon-gan. To keep the heavy stress on the "o" after adding le, we have to write it as pónganle.

Why use le here? Doesn't le usually mean "to him" or "to her"?

It often does, but le is an indirect object pronoun that can also mean "to it". In this sentence, they are putting the bandage on the wound. The wound (la herida) is the indirect receiver of the bandage, so le is used here to mean "on it".

Since la herida is a feminine noun, shouldn't the pronoun be la instead of le?