Then from my understanding it won't be very easy to add key-less entry to the car.
If your car doesn't have the key-less system, you'd need the alarm module, wiring harnesses, immobilizer, reprogram the BCM/ECM (maybe even replace it if it's a different model that's required), keys (fobs are integrated into the key for most years), and I'm not sure what all else would be involved.
If your car has the system, and you need a "fob" you're best bet would be to have a dealer help you. Aside from that, I'm not sure you'd really want to undertake that project.
The Aveo is an Economy class car, and even in the later years people bought Base Models and the only thing it had was usually an Automatic trans, and maybe AC. I realize people are sometimes limited on what they can afford, but a mid level trim is usually not much higher and includes a lot of the little niceties like Key-less entry and some power options. Especially for something as cheap as the Aveo, was/is.
Because of that I never understood why people will by a base model, (I'm not targeting you since I don't know what year the car is or if you bought it new, etc.) I'm just saying this is an issue people run into when they decide the want something and realizing that it's done in production and can't easily be added.
I apologize if that seems rude, as it wasn't intended to be.
Best,