Let me drop back and get really basic with this.
A keystore is a file that contains information that can be used to encrypt your app to keep it from being easily stolen. It is referred to as "digitally signing" your app. It gives it a signature that makes sure you are actually you. This keystore is a file, stored somewhere on your computer.
There are two types: A debug keystore, used for testing. A debug keystore cannot be uploaded to a store. Then you have a release keystore that is used for stores. The debug keystore is named debugkeystore or something obvious. The release keystore you can name whatever on earth you want it to be. Each keystore also has an "Alias Name" (that honestly I don't know what it's used for, just that it has to match what you set up) that you have to define.
A key hash involves taking that keystore file and running it through a process that generates a short, unique and non-reversible "hash" of the keystore. This is the value that Facebook wants.
Problem #1. The command Facebook would have you run is for a debug keystore that is in the Android SDK file somewhere. Corona SDK, when you build with a debug keystore uses one located in the Corona SDK folder. This debug keystore is different than the the Facebook's instructions gives you. Facebook would have you do:
keytool -exportcert -alias androiddebugkey -keystore ~/.android/debug.keystore | openssl sha1 -binary | openssl base64
But that's not the right keystore. You need to execute:
cd /Applications/CoronaSDK/Resource\ Library/Android/
keytool -exportcert -alias androiddebugkey -keystore debug.keystore | openssl sha1 -binary | openssl base64
Then if you build using a debug keystore in Corona you will have the right value. But....
You cannot deliver this app to a store for other people to get, so you need to use a release keystore. I have no idea where on your hard drive you have it saved (if you have one). I have no idea what alias you gave it. But you should use the "cd" command and change to the folder where it's stored then execute the keytool command above substituting the alias and keystore values for what you already used. Then you make sure to build against it. Whatever keyhash you build with is what you need to tell facebook.
Now if the log file has the keyhash you need, you can just copy it (It may need an = sign on the end). For more details on this, we wrote an extensive tutorial for facebook authentication: