Hi.
The 'key' is a reference to that variable so if you call it "CharacterSelected"
Then you need to use that reference to read or change the value.
The value is the int variable for your selected Character.
So after you selected a character (for example character 3) then you can set that value by using 'PlayerPrefs Set Int' key : CharacterSelected Value : 3 (best to use a variable instead of a number)
in the next scene use 'PlayerPrefs Get Int' key : CharacterSelected and use a variable to get the value (which will be 3)
Now you know Character 3 is selected in the other scene