What motor are you using?
If you are using blind motor you will need the remote control that should comes with it when you purchase it. If you dont have the remote you can buy it from aliexpress or pair it with a tuya hub and use the tuya app to set the limits.
If you are using curtain track motor you need to install it on the track and the motor will automatically set the limits when it senses the physical limits (i.e. fully close or open).
Ask the motor seller for the manual which will instruct you on how to set the limits.