Simple. You simply use Roman characters (English letters). Japanese is a very simple language to write out, it is completely phonetic. That is to say, that it is written exactly how it sounds. If you wanted to write the Japanese phrase for "Congratulations" in Roman characters, it would look like this... "Omedetou Gozaimasu". Very simple.
You could acquire a proficiency in the language that allows for it, request the help of a Japanese speaking friend, or pay for the services of a translator. Automated internet based translation software is not reliable in Japanese, and often spits out nonsense phrases, or fails to capture the intended meaning.
You can use translation services online, I'll provide a link for one below.
But if you are asking 'you' as in myself then I have studied Japanese for 4+ years and can translate for myself or ask friends if I do not understand the Japanese.
You use romaji.
As in 咲いた花 would be saita hana, or Blooming flower.
If you search a Japanese word in Google I'm sure it will come up with something that has the symbols on it
I don't know the English translation but you can get it here translate.google.com/
Japanese is made up of phonemes/syllables. All kanji/kana are made up of these syllables. These syllables can then be represented in English characters called 'romaji.'
http://translate.google.com/translate_t
日本文書
Nippon bunsho
what its means
Nintendo64
The words "little bomber" translate to _____ in Japanese. There are many translators online that can easily translate words from English to Japanese.
Very carefully.
cannot translate this one its not English or Japanese
Aslan
O-Genki Desuka.
Heart.
This can translate into English as "Because I can't forgive".
The word "uprising" in English would translate to "Bōdō" in Japanese.
You can't I don't think.
An online translator.
Any Japanese to English translator should work translating a haiku.