If you want to change/remove footer link, please consider purchasing theme on http://www.simplewpthemes.com, and gain access to support forum at the same time. To remove this message just restore theme files via FTP.
1. Download theme from your account page: https://www.simplewpthemes.com/account/
2. Upload the theme via FTP client ( Filezilla,SmartFTP,WinSCP) – If you already have installed free version of Ceckito theme you must “overwrite”/replace old files with new ones.
How to Install Your WordPress Theme Manually Using FTP for the Absolute Beginner
Let us know if you need further assistance with this