My transcript has the wrong course names. How to fix this in PhD applications?
If at all possible you should get the issuing university to correct your transcript. Failing that, you should get a letter, signed by an authority, that explains the situation. The letter should come from some official. In the US, the person would normally be called the Registrar, but I doubt that is universal. Whoever is responsible for transcripts.
The answer of Nicole Hamilton is correct in that you shouldn't try to alter any official document.