HOW TO GET VISA FORM FOR CHINA VISA?

MY NAME IS EJIKEME.A NIGERIAN DOING BUSINESS BOTH IN NIGERIA AND CAMEROON.I SALES ELECTRONIC.
I MET A FRIEND IN DUBAI ONE MONTH AGO,HE WAS GIVING ME IDEA THAT IT IS BETTER FOR ME TO GO CHINA
AND BUY DIRECTLY FROM FACTORY.AND I HAVE A COMPANY THAT PROMISE ME TO GIVE ME AN INVITATION LETTER.
I WANT TO ASK WHETHER IT IS IN ABUJA THAT I WILL FILL THE VISA FORM WHEN I GET THERE WITH OTHER
NECESSARY DOCUMENTS OR AM I SUPPOSE TO GET IT BEFORE GOING TO ABUJA FOR INTERVIEW?. THANKS,WAITING FOR YOUR REPLY.