Learn Hardcore Norwegian: Hun åpner skapet.

Hun = the subject pronoun, she
åpner = the verb, in the present tense, opens / is opening
skapet = the object, the definite form of skap, meaning the cupboard / cabinet / closet depending on context

So the structure is:

subject + verb + object

which is very similar to English.

Why is skapet one word instead of something like the skap?

Because Norwegian usually puts the definite article at the end of the noun instead of using a separate word before it.

Here:

So skapet literally means the cupboard as a single word.

Why is it åpner with hun? Shouldn’t the verb change for she?

No. In Norwegian, verbs do not change according to the subject the way they do in English.

In English:

In Norwegian, the present tense stays the same:

So åpner is correct for all persons in the present tense.