Finding the right symbol
Is there a system on the keyboards to find the right symbol?
Do you mean Chinese characters like 汉字?
Or do you mean pinyin like lǜsè?
For the Chinese characters you have to use a Chinese input method that converts your typing into characters. You don't need to change your keyboard layout for this.
For the special letters and diacritics used in the pinyin transcription you may need to change your keyboard layout.
Please be more specific: what Operating System are you using?
On iOS, it's easy to add a Chinese keyboard. Actually, there's at least 3 Chinese keyboards: 1. pinyin 2. handwriting recognition! 3. I'm not sure what the 3rd one is.
I've also just installed the Google pinyin on my Linux box and it works!