Drat! You've named your character Johnathan and just now realized that Johnny would've been better. We get it.
On Windows just use CTRL+F, or if you're on Mac, CMD+F to open the Find/Replace toolbar. Or select 'Find & Replace' in the Edit Menu.
The arrows can cycle forwards and backwards through instances of the word you searched.
'Replace' will replace the word you find with the text you put in the Replace field. Leave the Replace field empty to simply delete the found text.
Use 'Replace' All to replace or remove all instances of the found word.