I already have a wyze sense with motion and 2 door sensors. Can I add another motion and door sensors, how and by them individually?
you can always add more to your mix. However, Wyze has stopped the Wyze Sense V1, assuming you are talking about these. They are getting ready for the new V2 sensors with hub.
With that said, if you currently have some, you can simply go through the process by using the provided pin and pushing it into the sensor to start the pairing process. During this process, you will be prompted which bridge to connect it to. Select the Camera which has the V1 Bridge in it.
If you need more sensors, I think you will need to get a bundle pack which includes some of these sensors, or check at places like Home Depot.