You know the subject. It is only that you should be little bit more confident.
Pray 5 times & read Quran daily with translation daily.
When you enter the hall read always RABB E ZIDNI ILMAN & start with BISMILLAH.
Read your question sheet first. Do not hurry to reply. Take 5 minutes to decide which question you can answer best.
Then start writing.
INSHALLAH if you get practice at home you will be confident.