Learn Portuguese (Portugal): Quero ver o museu.

The word for 'I' is eu, but it is often dropped in Portuguese. The verb form Quero already tells us exactly who is doing the action, so saying Eu quero is correct but usually unnecessary.

Why isn't there a word for 'to' between Quero and ver?

In English, we say 'want to see'. In Portuguese, the 'to' is already built into the dictionary form of the second verb, ver (to see). You just put the two verbs right next to each other without adding anything in between.

Why doesn't ver change to match the speaker?

When you combine two verbs like this to say you 'want to do' something, only the first verb (Quero) changes to show who wants it. The second verb (ver) stays in its original dictionary form, which is called the infinitive.

Can I just say Quero ver museu without the o?

No, Portuguese almost always requires definite articles like o (the) before nouns in this context. Since you are talking about a specific museum, you must use the masculine singular article o before museu.