Learn Portuguese (Portugal): O sabão está no lavatório.

In Portuguese, we use the verb estar (which está comes from) to talk about the physical location of objects and people. We use it here because the soap's location is temporary.

How does no mean "on the"?

The word no is a mandatory combination of the preposition em (which means in, on, or at) and the masculine word for "the", which is o. Because lavatório is a masculine word, we shrink them together into no.

Does no mean "in the" or "on the"?

It can mean both! Portuguese doesn't strictly separate "in" and "on" like English does. Depending on the real-world context, no lavatório can translate to "in the washbasin" or "on the washbasin".

How do I pronounce the ão in sabão?

The wavy line over the "a" is called a tilde. It tells you to pronounce the vowel sound through your nose. The -ão ending sounds a bit like the English "ow" in "cow", but nasalized.