I do not have direct experience of the bzl , but it looks similar mounting to my RS6
First step is to drop the drive belt from the motor pulley.
Second step is to electrically disconnect the wires from the motor terminal box ( mark the connections for later re-connection ) Ensure the lathe is physically disconnected from the power source before doing any electrical work.
If your motor is three phase, label L1 L2 and L3 on the motor terminals and the input cables. If you get this wrong, your machine may run in reverse. No problem, just interchange any two input lines.
The third step would be to either unbolt the motor feet from the plate and remove the motor.
Depending on the ease of access, you may find it easier to remove the motor and plate together by driving out the hinge pin. On the RS6, it was easier to remove the motor - even though the original motor was VERY heavy
There are several sources of info for this lathe - just google wadkin bzl manual pdf
This should be a simple job - so hope this is of some help