No, doesn't have to be bolted.
If it is the Apexi this doesn't even provide the facility to bolt to the floor.
See pin-out below. Main Power is Connector B136 Pin 8 and 9 and B136 Pin 25 from Ignition switch.
Be careful as not sure if diagram is a view of the ECU connector or the attached cable connector (i.e mirror image)
Match the keyway/pips positions on your connector to the diagram below.
Piccies from JGM site, as can't access mine from the office.