# How can I identify and draw the optical isomers for all the isomers of [Co(NH_3 )_2Cl_2 ]^-

Quite possibly you mean, ${\left[C o {\left(N {H}_{3}\right)}_{2} C {l}_{4}\right]}^{-}$, i.e. an octahedron, not a tetrahedron.
As written, the cobalt complex would not support optical isomerism. The Co(III) complex, ${\left[C o {\left(N {H}_{3}\right)}_{2} C {l}_{4}\right]}^{-}$, would support geometric isomerism; it may be cis or trans with respect to the ammine ligands.