Installing a hitch on most small cars is not difficult. As an example, etrailer.com shows two hitch options for your 2019 Leaf.
The more important question is how much weight you want to carry? Different folks will have different opinions, but I wouldn't want to go above 150 lbs (including the weight of the cargo tray/box). You'll also want to stay within the rated payload capacity of the Leaf, which is something like 985 lbs and includes the weight of all passengers and cargo in or on the car. Finally, you'll want to make sure your cargo doesn't block your rear lights and recognize that you will most likely block your rear-view camera.
