warukanai yo.
(And by the way, it'd be muzukashikute, warui da~)
There's this thing where you type in pinyin and a list of the zhongwenze comes up and you pick one.
Alternatively, when typing in pinyin a lot of people just go by context. Or, if you're like me, you type out the tone after the word.
xiang4 je4 yiang4 zuo4. je4 bu2 shi4 yi2 ge4 hao3 de4 ban4 fa3 yin1 wei1 xie3 he2 du2 (haha there's that du) do1 hen3 ma2 fan4 -- dan1 shi4, wo3 hai2 ting2 xi3 huan4
(If the pinyin is mispelled sue me, I can't type in pinyin worth crap)
一个大西瓜