Learn Swedish: Andas ut genom munnen och blunda. - Breathe out through your mouth and close your eyes.

Andas is an s-verb. To form the imperative of an s-verb, you take the normal imperative form and add -s. Since the base here is anda, the imperative becomes andas. For these types of verbs, the imperative often looks exactly like the present tense and infinitive!

Why does the sentence use munnen (the mouth) instead of translating "your mouth"?

In Swedish, when it is obvious whose body part is involved in an action, you use the definite form of the noun instead of a possessive pronoun. Since you are the one breathing, Swedish simply says munnen rather than din mun.

Why is there no word for "eyes" in the Swedish sentence?

The Swedish verb att blunda specifically means "to close one's eyes". You do not need to add the word for eyes (ögon), because it is already built into the meaning of the verb. The imperative form is simply blunda.

How does the pronunciation stress work with andas ut?

Andas ut is a particle verb meaning "to breathe out" or "exhale". Like most Swedish particle verbs, the emphasis in spoken Swedish falls on the particle, so you should stress the word ut rather than andas.