Hello Furkan,
I understand the inconvenience.
Please do not share your email address on a public post.
If your PC TuneUp program doesn't have an option to enter the license number, it is necessary to uninstall it.
For uninstallation, refer this article: http://avgread.me/1DEtNP0 .
To install AVG PC TuneUp, follow the steps as mentioned (here) and it will ask for license number to be entered.
Feel free to contact us if you need further help.