Just as Rick said, show what you have tried ,that is benefit to you and us .
Check if the following code is what you need .
proc iml;
A=j(8,4);
call randseed(12345678);
call randgen(A,'normal');
cov=cov(A);
idx=loc(row(cov)<col(cov));
cov[idx]=-cov[idx];
skew_symmetric_matrix=cov;
matrix_rank=round(trace(ginv(skew_symmetric_matrix)*skew_symmetric_matrix));
print skew_symmetric_matrix ,matrix_rank;
quit;