Learn Spanish (Latin America): Yo quiero tener una vida mejor.

When you want to talk about an action you desire to do, you combine the conjugated form of querer (like quiero) with the infinitive form of the action verb. Here, yo quiero tells us who wants it, so tener (to have) just stays in its basic dictionary form.

Why is it spelled quiero and not 'quero'?

Querer is a stem-changing verb. When you conjugate it in the present tense for most subjects (like I, you, he, she), the e in the stem changes to ie. That is why it becomes quiero.

Do I need to include yo at the beginning of the sentence?

No, you can drop it and just say Quiero tener una vida mejor. Since quiero only ever means 'I want', the word yo is optional and is usually just included when you want to add extra emphasis.

Why does mejor come after vida instead of before it?

In Spanish, adjectives (descriptive words) usually come right after the noun they describe. While mejor is one of the few adjectives that can also go before the noun (as in una mejor vida), putting it after (una vida mejor) is very common and sounds completely natural.