Learn French: Tu veux un nouveau travail.

Vouloir (to want) is a highly irregular verb. For the tu (you, singular/informal) form, it is spelled veux. The je (I) form happens to look exactly the same: Je veux. In both cases, the "x" at the end is silent!

How would I change this to say "He wants a new job"?

You would say Il veut un nouveau travail. Notice that for il (he), elle (she), or on (we/one), the verb changes from veux to veut. It still sounds exactly the same out loud, but it is spelled with a "t" instead of an "x".

I thought French adjectives usually go after the noun. Why is nouveau before travail?

You are right that most French adjectives go after the noun, but there is a small group of common adjectives that go before it. A handy way to remember them is the acronym BANGS: Beauty, Age, Number, Goodness, and Size. Nouveau (new) falls under "Age", so it jumps in front of the noun.

Why use nouveau here instead of nouvelle or nouvel?