How do I change the language or type accented characters?
The keyboard layouts provide keys for accented characters like ä or è, but if you have autocorrect enabled you don't necessarily need to use them. Autocorrect will replace the unaccented equivalents with the accented versions if it recognizes the word.
If you need to type a word from a different language than you are using, you can do so either by using the Option key to access the same layout provided on Macintosh keyboards (see video here), or by pressing and holding a key that has a popup menu (video here). If you tap Option, these keys are shown by a dot in the upper left.