Here's the procedure from Remoresremotes.com....if you have at least 1 working key.
https://www.remotesremotes.com/product-p/g_512c.htm
KEY PROGRAMMING
Please make sure to read through the programming instructions completely before attempting.
You must have one (1) factory key that can start the vehicle to perform this procedure. If you do not have one (1) factory key for the vehicle currently, a trip to a dealership or an automotive locksmith will be required for the programming.
1. Enter the vehicle and close the driver’s door.
2. Using a working factory key, insert the key into the ignition and turn it to the ON position as far as it will go without starting the vehicle, wait one (1) second, then switch it OFF.
3. Remove the key from the ignition.
4. Insert the new key into the ignition and turn it to the ON position as far as it will go without starting the vehicle.
5. The key is now programmed.
6. Test the key to ensure that it starts the vehicle. If the key did not program, restart the programming procedure from STEP 1. To program additional keys, repeat the entire procedure.