Before you ReFile, you must wait to receive your Notice of Assessment in the mail. Once you receive it you can verify that CRA hasn't added this amount on your return already. If not then proceed with ReFile.
You will find your return and it should say "REFILE" beside it- Click on ReFile - open your return up go to your "Personal Profile" and go continue until you see the question close to the bottom of the page "did you make tax installment payments for 2019? Click on YES which will open another part where you will enter the amount. Then click on continue and you can then go to the "File" section it will ask you to pay $5 dollars then you will be able to NetFIle once again.
