Learn Swedish: Jag vill ha det andra äpplet.

In Swedish, you cannot just say "want" (vill) followed by a noun like an apple. If you want a physical thing, you must use vill ha, which literally means "want to have". You only use vill by itself when it is followed by an action word (a verb), like jag vill äta (I want to eat).

If äpplet already means "the apple", why do we need det at the beginning?

This is a classic Swedish rule often called "double definiteness". When you put a descriptive word (like andra) before a definite noun, you need both the standalone "the" word (det) AND the ending attached to the noun (-t or -et on äpplet). So you are literally saying "the second the-apple".

Why do we use det here instead of den?

It depends on the noun's gender. Because apple is an "ett" word (ett äpple), the standalone "the" must match it and become det. If the noun were an "en" word, like en bil (a car), you would use den, as in den andra bilen (the second car).

Does andra mean "second" or "other"?

It actually means both! Depending on the situation, det andra äpplet can translate to "the second apple" or "the other apple". Without any extra context, either translation is perfectly normal in Swedish.