Sorry, this camera model is not designed for different lenses. The lens is "built in" - there is no procedure to remove it and put a different lens on the camera body.
In order to use different lenses you need a different camera body model. Since you are looking at the Canon 75-300 lens, consider the Canon camera bodies. You can get a used or refurbished older Canon body for a very reasonable price as everyone is always trying to move up to the newest bodies and selling their old bodies on
eBay and
Craigslist. Just beware of deals that look "too good to be true" because they are usually scams!