Help:How to type in Korean
It can be daunting at first, but don't be discouraged. The key is to remember that input method editors are smart. This is the hardest part: It is up to you put in spaces between things like 저는 and "김민수"입니다, but if you forget, it is s not incomprehensible. Also, if you break up compound words, it won't impede understanding. However, in English spacing I smore import ant than ink Orean. Korean letters are read according to predictable rules and writing 저 는 마 크입 니다 is still pronounced the same as 저는 마크입니다.
As you type, the engine will know whether you typed 좋았어 or 좋아써 because you are typing ㅈ ㅗ ㅎ ㅇ ㅏ ㅆ ㅇ ㅓ vs ㅈ ㅗ ㅎ ㅇ ㅏ ㅆ ㅓ. They both sound exactly the same, but as you type you will notice that the input method editor will instantly shift 받침 based on what you type next. When you get the hang of it, it is rather quick and painless. Because all consonants (including the null/ng consonant ㅇ) are on the left and all vowels are on the right and the shift key is used sparingly, you will find you can type very fast. All jamo blocks will be CV or CVV or CVC or CVVC. If your text looks wrong, make sure you are typing your diphthongs in the correct order (와=ㅇㅗㅏ) and make sure you are using your nulls properly (먹어=ㅁㅓㄱㅇㅓ).
Just hit the 한/영 key to switch typing modes on a Korean keyboard, or the right Alt key on a 101/104-key keyboard. If you want to use hanja, just type the syllable block and hit the 한자 key while the block is still flashing. You can't go back to a block you've already typed and change it unless you delete and retype that block. The 한자 key is not like a Caps Lock. It only transforms the block which is flashing. It's designed to be used on a case-by-case basis. If you need to do batch conversions from hangul to hanja you need a smart program since some characters may have variant pronunciations. For this you might need the Hancom Office products. I do not recommend using them unless you're advanced; they handle internationalization and text alignment very poorly. I advocate spreading awareness of .pdf or .docx files in Korea anyway.
LibreOffice is a free, open-source program that handles Unicode perfectly as is a nice drop-in replacement. The look is modeled after Microsoft Office 2002, but expect a lot of progress in the development. Since the developers and volunteers left Oracle's Openoffice.org (now defunct) it has accelerated. It is available for PPC Macs, Intel Macs, Windows-Intel, and Linux.