I wanted to know if there is a website/link that I can refer to for understanding how the entire LAMMPS code works like source code browser/navigator. I have gone through the LAMMPS developers manual and other associated documents but I feel it would help if I know which classes the code goes through for each type of run so that I can modify the code appropriately for writing a fix.
Read the instructions in the manual about adding a fix style
Read the comments in fix.h
Look for a fix style similar to what you want to implement and read it and experiment with it
Use that fix as a template fir your fix
Lammps is designed so you don’t need to know about the rest until you want to do something very complex, but in that case, you should practice with something simpler first.