Like
@Brian Dean said, you are asking too many questions.
You are stucked on how to proceed and you feel worried.
Stay Calm.
You can't start programming when you are not clear what you need to do.
Knowing SDLC may help you on this.
You need to do analysis of the requirements and plan your strategies.
Break the big problem into small parts.
Work from one part then move on to the other parts.
Always try to start small and simple.
Use whatever you have now.
I suggest you break the problem into 2 parts.
1. Backend/Server
2. Frontend/Client