How to set a breakpoint in gdbgui?

I have a fortran file that I compiled it in this fashion:

gfortran -g -fbacktrace -ffpe-trap=zero,overflow,underflow youcode.f90 -o run.exe

So I do have a run.exe file coming out. I started gdbgui --args run.exe. I found a place to load the .f90 file and have the fortran text come up. I looked all over for a way or button to set a breakpoint and run the .f90 file which is a working hello style fortran that prints a line of text to ther terminal. How might I set a breakpoint and have gdbgui run to that line?