If your unbalanced gear uses an unbalanced jack input (TS connector), then you should use an unbalanced jack cable to connect iD22 to the outboard gear for both the sends and returns.
It is possible to use iD22's balanced insert points with unbalanced gear that uses XLR input however some rewiring of a jack cable could be needed to get it to work. The cold wire (blue in diagrams) needs to be soldered to the sleeve (ground) wire.
Unbalanced XLR to Balanced Jack:
The balanced connector must be plugged into the send or return sockets of the iD22.