You must have an ammeter function in the multimeter. Disconnect positive connection to the battery turn the amp meter to the highest setting then connect the + lead from the meter to the battery and the - to the post. Power will flow through the meter and on to the circuit. This function is usually fused because it can easily blow your meter if the current flow is to large (short to ground). If you get a low are minimal reading, turn to next lower setting until you can se what the current flow is.
There is one other way but very much more expensive. They make a conductive coil that can be attached to the meter to show current flow. It will make it so the current does not flow through the meter and save the potential of blowing the meter.
There is one other way but very much more expensive. They make a conductive coil that can be attached to the meter to show current flow. It will make it so the current does not flow through the meter and save the potential of blowing the meter.