Since HCN is not found naturally, it must be manufactured.  There are several different ways to make HCN, 

Two ways that are easy to do:

One way is to pass electric sparks through C₂H₂ and N_2.  The combination of these two compounds forms HCN

C₂H_2(g) + N_2(g) ^{à HCN (g)}

^{Another way is by the action of HCl on a metal cyanide, one example of that is}

^{KCN(s) + HCl(aq) à KCl(aq) + HCN(aq)}

^{Since HCN has a lower boiling point than KCl you can evaporate the HCN from the KCL and then collect the HCN gas.}