我如何使用ASP.NET在web.config文件中的appSetting中编写？

I can easily read my appSetting in web.config file and then fill all keys and values in asp.net form. but I need to have initial setup for my web application how I can write in appSetting ? Is it the best way or not I have to store all of the keys in database which is better ? and How I can implement this ? I need to add a key and edit a key or their value in appSetting config file.I can easily read my appSetting in web.config f