[Chimera-users] distance between 2 residues

Dear all, I would like to know the (mean or approximative) distance between two residues within a protein (let's say Res 5 of chain A and Res 246 of chain C). I suppose that I have to select one atom in each of the residues and use the Distance tool. I confess I have trouble to do so, either by picking in the viewport or by using the atom identifier. May you tell me a simple way to achieve such a distance? Many thanks for your help Damien