For the TSM Desktop Application, you can uninstall the program through 'Add or remove programs' menu in Windows, or via the uninstaller located in the application directory - the default directory is Program Files (x86)\TradeSkillMaster Application
For the TSM Addon suite, you can remove the TSM Addon folders from your Interface\Addons directory to 'uninstall' the addons. If you would also like to remove all of your settings you can remove the TSM Addon saved variables as described in the following article:
Where are my TSM Settings stored?
All addon (and game) settings are stored in your 'World of Warcraft/GAME_VERSION/WTF/' folder. Specifically, TradeSkillMaster stores its settings in a file within the 'WTF -> Account -> ACCNAME -> SavedVariables' folder under _retail_, _classic_, or _classicera_ with the file being named TradeSkillMaster.lua.
Be sure you have WoW completely closed before messing with these files or else your changes may not have any effect. We cannot provide support for, and do not recommend, making changes or modifications to these files.