How to install Freon?

You are looking for the low side connection if you are using one of those fill cans.

Here are a couple guides that will help locate these:

https://www.2carpros.com/articles/air-conditioner-how-to-add-freon

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

This fitting is going to be on the low sideline. However, we don't have a location view on this. So, I am attaching a picture of where they should be.

Take a look at this and if you still can't find it then get some pictures of your engine bay, specifically the A/C lines and components and we will find it.

Thanks