find process address pointer + offset

[heiron]

Hi,
I have this code

while (!ReadProcessMemory(hProcess, (LPVOID)dwLocation, &FirstByte, sizeof(FirstByte), NULL) || FirstByte != 0x55)

I want to read from a process the First BYTE, I want to find the dwLocation of the process, I know it is process.exe + offset = address, how can I find them? shall I use a debugger or something?

Thank you