You are an English major, so you don't need to do any preparation.
First of all, you should confirm whether your self-taught degree is recognized there. At present, only big cities such as Beijing in China recognize this kind of equivalent academic ability, so you should think it over; Secondly, I think the key school for English majors is Beijing Foreign Studies University, where the self-taught examination has formed a large scale. Why not choose to come to Beijing with more resources?
hope this helps