Locate the fuel injector you wish to test, you do not need to remove the injector to test
Now locate the wire clip. Each plug has one of these.
Press this wire clip in towards the injector and then wiggle and pull the plug. Do not pull on the wires.
Set your test meter to the lowest ohm setting, skip that if you have a auto scaling meter. And put one probe on each terminal.
You should have about 11.7 to 12.0, all injectors should be close to the same.