NVM or NCM? (title says one, posts says the other)
NCM C5 via google brings up this
Built for those that want to electrify their commute and experience a more convenient way to get around, the NCM C5 e-city bike makes your daily rides around town smoother, simpler and more fun than ever, fitted with a torque sensor for a seamless pedal feel and superior range. BIKE...
ncmbikes.com
Is that what you have? If so, it says it uses a Das-Kit CT-I6 controller.
Nothing comes up for a website for Das-Kit itself, and none of the sites that do come up with that brand of stuff for sale have any technical info on the controller at all, nor any manuals for them, or labelling for the connectors and pins, so I don't see any way to know whether or not the controller supports a throttle or not.
Some systems that don't come with throttles are programmed in the display and/or controller to not accept input from one even if you solder in wires to one to the appropriate pads on the controller PCB...so yours might not, or it could.
You can always change out the controller and display of your bike to any controller/display set that does accept a throttle, such as the KT Kunteng series, or LS LiShui series, or various others. Make sure you pick one that is for 36v, and has a current limit of 15A, to match what you have now so it does not stress your battery/etc.
The connectors on it might not be the same as those on your bike, so you may have to change connectors on either bike or controller to fit each other, and figure out wiring for each such connector that must be changed. (even if the connectors are identical, it does not mean that they are wired compatibly, so you should see if your bike manual says which pin is which, or see if the manufacturer will tell you. If not, you may have to open things and check, or just plug things in and hope for the best (which can damage things if the wiring is wrong).