Yeah, press ctrl+x then enter then ctrl+\ (not /), that's C-x RET C-\ in Emacs notation, then, for tab you need to remap one of the keys to be tab, I'll post about that later, in the meantime, you need to type the full name of the input method without tab.

For chinese, GNU Emacs has the following input methods:
chinese-4corner
chinese-array30
chinese-b5-quick
chinese-b5-tsangchi
chinese-ccdospy
chinese-cns-quick
chinese-cns-tsangchi
chinese-ctlau
chinese-ctlaub
chinese-ecdict
chinese-etzy
chinese-punct
chinese-punct-b5
chinese-py
chinese-py-b5
chinese-py-punct
chinese-py-punct-b5
chinese-qj
chinese-qj-b5
chinese-sisheng
chinese-sw
chinese-tonepy
chinese-tonepy-punct
chinese-ziranma
chinese-zozy

So after C-x RET C-\ just type one of these full names and hit RET.

GNU Emacs will then switch into the input method and you'll be able to type Chinese.

To switch back and forth between the selected method and English then, just hit C-\

If you need to select another one, do C-x RET C-\ again.