You mean like this? はじめまして
If so, you can type like that on your smartphone or your Windows or Mac computer.
There are four writing systems you should learn:
-Hiragana
-Katakana
-Kanji
and Romaji, which is the writing of Japanese using the roman alphabet. (ex: nihongo wa muzukashii desu)
Usually, to allow your device to type in hiragana/katakana/kanji, you have to go into setting and the keyboard settings and add an input source or character set. I can't help more without knowing what type of system you have!