build a project using given obj files

[TheCPUWizard]

I think he did not write a main function when generating the obj files. The reason is through the interface he gave me I should write my own main to do testing. If he did write a main, I would not be able to test as a program cannot have two mains. Am I right?
I wrote my own main.cpp which includes all header files. In this cpp I wrote int main() { return 1;}

You may think you did...but...the linker is not seeing it.

Most likely, you did not include the file in the linker command, possibly you declared main as having file scope, maybe you even spelled main wrong. Please SHOW your implementation of main.