How to run specific modules in LAPACK in a Fortran code?
With the title "Using LAPACK library in fortran codes" in this forum, it is clearly explained.
Use call option to find the solution for the A*X = B lenear equations using the routine DGESV
call DGESV()
Compile the code by
gfortran -o output codeName -L. -lliblapack
From LAPACK page, 
"DGESV computes the solution to a real system of linear equations
    A * X = B,
 where A is an N-by-N matrix and X and B are N-by-NRHS matrices.
 The LU decomposition with partial pivoting and row interchanges is
 used to factor A as
    A = P * L * U,
 where P is a permutation matrix, L is unit lower triangular, and U is
 upper triangular.  The factored form of A is then used to solve the
 system of equations A * X = B. "
